The concept behind HESSI (as it was originally known) began in the 1970′s, but it wasn’t until 1997 that the technology and knowhow became available for it to finally be chosen by NASA to be built. Ahead of schedule and under budget, HESSI was set for launch on 4 July 2000 until disaster struck during pre-launch tests being carried out at JPL. The ‘shake-plate’, designed to mimic the vibrations experienced during launch, was set too high and the solar panels and telescope mounts were badly damaged. Despite this setback, the satellite was ready for launch 6 months later in December 2000, although more delays pushed it back to 7 June 2001. Just 6 days prior to launch, another setback occurred. The Pegasus rocket that was to carry HESSI into orbit went out of control during a test flight. This delayed the launch even further to 2002. But the saddest part of the story came just months before launch when Reuven Ramaty, a key figure in the design and construction of RHESSI, and a pioneer of gamma-ray astronomy, passed away. It was in his honor that the ‘R’ was added to HESSI’s name, and RHESSI remains the only NASA mission to be posthumously named after one of its scientists.

Originally designed to last for 2 years, RHESSI is still revealing new insights into solar flares a decade later. Having observed almost 60,000 flare, there are almost 1000 refereed publications that utilise RHESSI data in some way, and many of them are highlighted in the recently released book, ‘High-Energy Aspects of Solar Flares’. Some of these highlights include discovering that electrons and protons deposit their energy in different locations through the first ever gamma-ray imaging of a solar flare; we have seen high-energy radiation high up in the corona during certain events pointing to the energy release site itself; and that interplanetary proton storms are generated by flares themselves, rather than by CMEs which was previously believed. However, some of the most interesting findings from RHESSI had nothing to do with solar flares at all. The three optical telescopes onboard which are used to stabilize the spacecraft were used to measure the oblateness (the ‘bulge’) of the Sun itself to an accuracy of 0.001%; something that will help broaden our understanding of gravity. RHESSI is also able to detect Terrestrial Gamma-ray Flashes (TGFs) which stem from lightening here on Earth, which RHESSI observes when it passes through the earth’s shadow. Once a year, RHESSI is also able to observe gamma-ray emission coming from the pulsar at the centre of the Crab Nebula, and in 2004 it detected one of the greatest gamma-ray bursts ever recorded from a magnetar (a neutron star collapsing under its own gravity).

This image is from one of my own pieces of work involving RHESSI data, and on which Alex was a co-author. It shows two X-ray sources high up in the corona merging together during a CME eruption. The merging occurred as the CME began to accelerate and appeared to result in intense radio emission implying that particle acceleration had taken place. This suggested that both the flare and the CME were driven by the same energy release at a location high up in the solar corona.

Although RHESSI is still continuing to function its germanium detectors are suffering from extreme radiation damage, and the cyro-cooler which keeps them cold is failing. In November 2007 the detectors were annealed for the first time to repair the radiation damage. This was successful and bought a few more years observations until 17 March 2010 when RHESSI suffered another anomaly. For reasons still not fully understood, something appeared to trip the safety circuits onboard the spacecraft as it flew through the South Atlantic Anomaly, which led to a complete shut down, including the heaters to the batteries which eventually froze. The skill and dedication of the engineers at the University of Berkeley, California where RHESSI operations are carried out, eventually led to RHESSI being successfully recovered, and after a second anneal, RHESSI was in perfect working order. Even two of the detectors which never fully worked since launch were working at optimal efficiency! At this time, RHESSI is undergoing one final anneal before the detectors are damaged beyond repair. This should enable high-energy observations to continue until the peak of the current solar cycle. After RHESSI, NASA has no future plans to build and launch a replacement and so routine observations of the high-energy emission from the Sun may not be available again for several decades. However, a balloon experiment (GRIPS) and a sounding rocket (FOXSI) which are based on RHESSI technologies are currently scheduled for launch in the next few months.

On a more personal note, I have had the honor and privilege to be a part of the RHESSI team for 4 years while working at Goddard Space Flight Center until I returned to Ireland this time last year, and I have been making use of its data since I began my PhD in 2003. The mission Co-I, Brian Dennis, has been a huge influence on my career in solar physics, and I regard many of the RHESSI team as very dear friends. I’m sorry that I’m not able to be at Goddard to be with them to celebrate this landmark occasion but I shall raise a pint of Guinness in celebration here in Belfast! I look forward to seeing what else this incredible mission can teach us, in conjunction with the rest of the solar fleet, as we approach the next solar maximum.

A sungrazing comet called Lovejoy is near what will surely be its end. Sungrazers melted by the Sun is not really new. In fact, SOHO has become the most prolific comet observer at over 2000 and counting. But what makes this special is that it is exceptionally big, about 100 meters, and so it will be exceptionally bright as it gets closer to the Sun. It has a lot more material to melt away and so sunlight is going to really light up the comet.

Comet Lovejoy observed in SOHO/LASCO C3 as it approaches the field-of-view of C2. (from http://helioviewer.org)

Comet Lovejoy (C/2011 W3) was discovered on December 2, 2011 by Australian astronomer Terry Lovejoy. He is an early pioneer in the discovery of SOHO comets and he discovered it both with a ground based telescope and with SOHO. This is only the second Kreutz-group comet observed from the ground and the first seen both from the ground and space. This makes Terry Lovejoy the first person to observe a Kreutz comet with ground and space-based telescopes.

Kreutz comets are thought to be the remnants of a single large comet that broke up several hundred years ago. Kreutz comets are a special group of “sungrazers” because their orbits are so close to the Sun that they evaporate. They take 800+ years to orbit the Sun. Here is its orbit as it approaches within 0.2 solar radii of the Sun’s surface.

The orbit of Comet Lovejoy as viewed from Earth.

Here is a video of the comet’s path from the PROBA2 team.

www.youtube.com/watch?v=dk2dQk0TKbw

Tonight (Thursday 12/15/11) at 7:30 pm ET Comet Lovejoy will reach perihelion. SDO, Hinode and Proba2 will try to observe Comet Lovejoy as it passes behind the Sun. Starting at 23:30 UTC (6:30 pm ET) the SDO spacecraft will point a little to the left of its usual position. The figure below shows the viewpoint of SDO where the circle is the edge of the Sun and the X’s are where we estimate the comet will be and the red arrow shows the direction the comet moves. From the viewpoint of  SDO the comet goes behind the Sun at 00:22 UTC (7:22 pm ET).

The trajectory with timing of Comet Lovejoy as seen by the off-pointed SDO.

All three instruments on SDO will be watching the comet. The EUV images from AIA would show the second comet seen in these ultraviolet wavelengths (the first was in July). HMI and AIA can use the comet to understand the roll of the spacecraft. EVE might see some of the atomic ions responsible for making the comet bright in the EUV.

STEREO/SECCHI and SOHO/LASCO have already been observing Comet Lovejoy. The hope is that  SDO, Hinode and  PROBA2 will also observe its demise as it is evaporated by the Sun. For SDO all three instruments will be watching the comet. AIA will take EUV images (like the first time a comet was seen in EUV in July). Both HMI and AIA will use their comet observations to understand SDOs roll. EVE will hopefully give us spectroscopic information about the composition of the comet.

To keep up with the observations you can check out the Sungrazer Project and the SDO comet page.

We will also add more images and video here when it is available. Also, there is always The Sun Today at Facebook. Stay Tuned!

Here are a few videos, more to come!.

STEREO HI-1A

www.youtube.com/watch?v=7Zjsy9gL8mE

SOHO LASCO C3

www.youtube.com/watch?v=sTMCi4KtbFo

SDO AIA

The first images of the comet! Faint but it is there!

www.youtube.com/watch?v=eyo7bE0Mrto

The aftermath:

SDO AIA

Here is Lovejoy after it has come back around. Still there!

www.youtube.com/watch?v=72DVbKyAfNQ

And another of it approaching the Sun.

www.youtube.com/watch?v=pPXGLgMenqA

SOHO LASCO C2/C3

Here is Lovejoy approaching and leaving the Sun in SOHO.

www.youtube.com/watch?v=FTj6O9H4ymQ

A montage of its journey including more STEREO and PROBA2

www.youtube.com/watch?v=lNuUevtgfn8

More soon!

Solar activity was at low to moderate levels, with occurrences of several C-class flares and three M class flares (see the list below). Quite a few slow to moderate CMEs were detected emanating from different regions of the Sun (some of them are listed below) throughout this week.

Flares (M class and above):

M1.1 from Active Region 11339 at 2011-10-31, 15:08:00  UTC
M1.4 from Active Region 11339 at 2011-10-31, 18:08:00 UTC
M1.2 from Active Region 11314 at 2011-10-31, 18:33:00 UTC

Here is a look at the full Sun from 10/27 to 11/02 in the 171 Angstrom wavelength channel of SDO

Earth directed CMEs (> 500 km/s):

First observed on 2011-10-27 at 12:24 UTC in the NE (upper right). The CME was observed in STEREO A/B and SOHO/LASCO. The estimated speed is 730 km/s with an angular width of 100 degrees.

Here is a look at the outer corona from 10/26 to 11/02. There are several CMEs including the one listed above.

Geomagnetic Activity

Geomagnetic activity was at low to unsettled levels, with the Kp index (ranging 0-9)

Outlook for November 2-8, 2011

Minor geomagnetic activity is possible due to solar wind streams. Sunspot group, AR11339, has the potential for increased activity as it moves onto the Earth facing solar disk.

resources: NASA GSFC Space Weather Laboratory, NOAA Space Weather Prediction Center and Max millenium Chief Observer

A close-up view of AR11339 as it rotates onto the Earthward side of the Sun

The visible Sun as seen by the HMI instrument aboard SDO. The new region AR11339 is large and growing.

Sunspot group AR11339 (AR stands for Active Region) has just rotated onto the Earth facing disk of the Sun. Before coming completely into view the region had produced two M flares in 24 hours (an M4.3 flare on 2-Nov-2011 at 21:52 UT and an M2.5 flare on 3-Nov-2011 at 10:58 UT). Here is another look at AR11339. This video is from the Solar Optical Telescope (SOT) onboard the Hinode spacecraft. (credit:Dr. Tom Berger)

The shape and complexity of an active region’s visible sunspots and magnetic field are the main indicators of its potential activity. These features are hard to see until a region has rotated fully into view but indications were that it had the potential of producing many C flares, a few M and maybe even an X flare. AR11339 has not disappointed! At 20:27 UT, November 3, 2011 it produced an X1.9 solar flare, 20 minutes before the drafting of this post.

GOES X-ray Emission over 6 hours

GOES X-ray Emission over 3 days

This figure shows the GOES X-ray emission over the past 6 hours and 3 days. At the end of each graph the X-rays rise to X1.9 then start to decrease.

It is too early to look at SDO images from the event. We will have to wait and see if this flare had an associated CME (coronal mass ejection) as well as wait to see what else AR11339 might have in store for us.

Shawn Malone took this photo of Aurora on October 24, 2011 in Marquette Michigan.

Saturday, October 22, 2011, started like most any other day, lots of activity of varying size and shape was occurring on the Sun. Most people looking at the Sun that day remember the spectacular lightbulb shaped CME that occurred from just behind the Northwest limb.

Here is the eruption and flare.

www.youtube.com/watch?v=6SuIPDEG78Y

and the resulting CME.

www.youtube.com/watch?v=FVAjkWX38vU

But it turns out the really interesting event originated from a filament on the solar disk just to the left of the more spectacular eruption. Just before the eruption that produced the lightbulb CME and filament eruption almost went unnoticed. The only real sign was after the filament lifted off. The magnetic field that tied the filament down, like a series of ropes tying down a long skinny balloon, was ripped away from the surface spreading outward. Where they were connected to the surface and pull away they left 2 expanding ribbons.

www.youtube.com/watch?v=5ioCJsiM26g

Once the filament left the solar surface it formed an irregular shaped CME directed toward Earth. It can been seen here in SOHO/LASCO and it occurred just before the lightbulb CME.

www.youtube.com/watch?v=Z6z9Kf3KkQg

It turns out that the filament contained a knot of magnetic field that was southward directed. This partially countered the northward magnetic field of Earth. This combined with the CMEs strong compression of the magnetosphere created a strong geomagnetic storm that generated aurora to low magnetic latitudes. This is why aurora were seen as far south as Alabama, USA. Aurora were seen around the world including in over 30 US states. Here is a great video illustrating what happened by Dr. Keith Strong of NASA’s Goddard Space Flight Center.

www.youtube.com/watch?v=xo6XwLFufrY

Many observers saw a red aurora. Red auroras are rarer. There is a nice discussion of red aurora by Carla Helfferich.

Here are just a few of the many Aurora photos taken by observers.

Many more can be found at the October 2011 aurora gallery from spaceweather.com.

www.youtube.com/watch?v=__2wPABzdpI

A spectacular filament eruption from June 7, 2011 captured by the STEREO Ahead spacecraft with EUVI 304, Cor1 and Cor2.

Happy Birthday STEREO!! October 26 ,2011 is the 5th anniversary of the launch of the STEREO mission and its 2 spacecraft. The STEREO Mission (Solar TErrestrial RElations Observatory) was launched at 1:52 am UTC on October 26, 2006 (8:52 pm EDT on October 25) on a Delta II 7925-10L rocket from Cape Canaveral Air Force Station in Florida. The 2 spacecraft were deployed from the single rocket and they moved into their orbits using the moon for assistance. This marked a great engineering achievement in orbital dynamics and the start of a great heliophysics mission that is still going strong today.

STEREO’s main overall goal is to help us understand coronal mass ejections (CMEs). So the first question is:

What is a CME?

As illustrated in this video, a CME is caused when magnetic energy is released on the Sun, flinging billions of tons of solar plasma into space at millions of miles per hour. When CMEs travel to Earth they can impact its magnetosphere causing the Aurora as well as potentially damaging spacecraft in orbit and creating electrical disturbances on the ground. These disturbances can cause disruptions in technology such as communication systems as well as electrical power grids. If the disturbances are strong enough, power systems can be completely knocked out. A famous example is the failure of the Quebec power grid for several hours in March 1989 following the impact of a strong CME on Earth’s magnetosphere.

But why STEREO?

STEREO provides us with detailed information about CMEs in never before seen details. In particular, what is their stucture? how big are they? how fast are they? Up until now we have only seen the CMEs that travel to Earth by looking at them head on. This makes it difficult to get a good measure of their features and characteristics. When you are looking at something moving straight towards you or away from you it is hard to easily measure its speed for example. This is even harder for CMEs because they are expanding and evolving as they move away from the Sun. STEREO has changed all that because it consists of 2 nearly identical spacecraft with viewpoints to the side of the direct path from the Sun to Earth.

Here is a discussion of STEREO by the Project Scientist for the SECCHI suite of instruments, Dr. Angelos Vourlidas. SECCHI contains the imaging instruments that show the solar disk (EUVI – Extreme Ultraviolet Imager), the outer corona (Cor1 and Cor2 – Coronagraphs) and the heliosphere (HI-1 and HI-2 – Heliospheric Imagers).

What is STEREO’s orbit?

STEREO spacecraft orbit generally along the Earth's orbit path. SOHO is about 1 million miles towards the sun from Earth at the Lagrangian Point L1.

In order to observe CMEs from the side the STEREO spacecraft were put into special orbits. One spacecraft, we call STEREO Behind, is to the left of the Sun (as you are looking toward the Sun from Earth) and the other spacecraft, we call STEREO Ahead, is to the right of the Sun.

This video shows the change in the spacecraft’s orbits over the STEREO mission.

Some of STEREO’s Accomplishments

STEREO has helped us make huge steps forward in our understanding of CMEs and their impact upon Earth. Here are some videos showing just a few of the many great results from the STEREO mission. We expect the mission to continue for many years and bring us an ever improving understanding of our Sun and its influence upon the Earth and the rest of the solar system.

STEREO showed us the first detailed interaction of a comet with a CME.

www.youtube.com/watch?v=cuFmgTGH9ds

Thanks to STEREO we can for the first time in history view the entire Sun.

www.youtube.com/watch?v=qLB5ma2Yz1I

STEREO has allowed CMEs to be observed all the way from the Sun to Earth for the first time ever.

www.youtube.com/watch?v=1kSx7AOwEco

For more information on STEREO check out the STEREO page in our solar mission hub. There is also a great article on the NASA site with some quotes from the STEREO Project Scientist and Deputy Project Scientist. More examples of the great science from STEREO can be found in the STEREO galleries on the STEREO web site.

We have been getting a number of questions and comments lately regarding the possible relationship between solar activity and geological activity, such as earthquakes and volcanoes, so I have decided to look into the matter in more detail.

First let us pose the science question we wish to answer: do solar flares cause earthquakes? Note that this is more specific than asking ‘is there a relationship between solar activity and earthquakes?’. First of all, solar activity can mean flares, or coronal mass ejections, or bursts of solar wind. Here I will focus only on flares, but do bear in mind that flares and CMEs often occur in tandem. Secondly, we are asking if flares CAUSE earthquakes; not whether a LACK of flares cause earthquakes. If flares do indeed cause earthquakes then we would expect to see a positive correlation between flares occurring and earthquakes occurring. If a lack of flares cause earthquakes, then we would expect a negative (or anti-) correlation.

For this experiment I have downloaded data from all known earthquakes from 1980 to the present day. This data is publicly available from the United States Geological Survey website (USGS). Here I must point out that I am not a seismologist – I have merely gathered together the dates and magnitudes of all known earthquakes greater than 4 on the Richter scale from the past 30 years. A list of all the solar flares from the last 30 years is also available from NOAA’s National Geophysical Data Center (NGDC). Below is the plot I made which shows the occurrence rate of both solar flares (in blue) and earthquakes (in red). (Anyone with a basic understanding of Excel, a little curiosity, and a bit of patience, can try this for themselves.) You can see that solar flares come and go with each solar cycle (approximately every 11 years), whereas earthquakes appear to occur continuously, with no obvious pattern. There are large (magnitude>7) earthquakes both at solar maximum and solar minimum. This to me would be evidence enough that flares and earthquakes are not related. But let us go a step further. What would something that IS correlated with solar activity look like?

The occurrence rate of both solar flares (in blue) and earthquakes (in red). (Click on Image to See A Larger Version)

What would something that IS correlated with solar activity look like?

For the next plot, I have gathered together data on the appearance of sunspots over the same 30 year period (http://www.ngdc.noaa.gov/stp/solar/ssndata.html; I happen to have access to a lot of solar data!). By overlaying the occurrence of solar flares on this plot, we can clearly see that the number of flares rises and falls with the number of sunspots (the orange curve), again every 11 years or so. I would call this a pretty strong case for proving that flares are in someway related to sunspots (which of course we know they are, as we can see flares occurring in regions of intense magnetic field on the Sun).

The occurrence rate of both solar flares (in blue) and sunspots (in red). (Click on Image to See A Larger Version)

I have also been looking at data on ionospheric disturbances here on earth as part of my own research (again, this data is publicly available via the Stanford University website http://sid.stanford.edu/database-browser/). I selected a day in which I knew there was significant solar activity (in this case, 18 February 2011) and plotted the solar activity for that day (top panel) against the corresponding changes in the upper atmosphere above Austria (bottom panel). This clearly shows that at least five of the flares that day (denoted by the vertical dashed red lines) had a direct impact on the ionosphere. Again, this suggests a causal relationship between solar activity and atmospheric disturbances; something not seen in the earthquake data.

The flare solar activity for 18 February 2011 (top panel) plotted against the corresponding changes in the ionosphere above Austria (bottom panel).

But these are large-scale statistical studies. What if there was one ‘perfect solar storm’ that happened to slip through the net? Would that then have any geological effects? Well, what is a solar flare exactly? The data I have used in the above plots are from X-ray sensors onboard the GOES series of satellites. So flares are essentially just that; increases in X-ray emission (and sometimes gamma-rays). There is, of course, increased emission from across the spectrum: radio, optical, UV, and infrared. Thankfully, the Earth’s atmosphere protects us by absorbing the vast majority of this radiation, as shown by the plot of ionospheric disturbances above. The only solar emission that makes it to the surface is visible light that we can see with our eyes, and radio emission (see figure below). So barely any of this X-ray light makes it through the atmosphere, let alone to beneath the surface to where earthquakes occur. Similarly, CMEs are essentially clouds of charged particles which get deflected by our magnetic field and rarely make it to the surface. And given that the Earth’s magnetic field has a strength similar to that of a household fridge magnet, any fluctuations caused by a CME impact cannot influence the motion of tectonic plates which carry entire continents!

This shows the what wavelengths of electromagnetic radiation can penetrate Earth's atmosphere and what wavelengths are stopped by the atmosphere.

We continue to be asked by many people throughout the world if earthquakes are on the increase. Although it may seem that we are having more earthquakes, earthquakes of magnitude 7.0 or greater have remained fairly constant.

A partial explanation may lie in the fact that in the last twenty years, we have definitely had an increase in the number of earthquakes we have been able to locate each year. This is because of the tremendous increase in the number of seismograph stations in the world and the many improvements in global communications. In 1931, there were about 350 stations operating in the world; today, there are more than 8,000 stations and the data now comes in rapidly from these stations by electronic mail, internet and satellite. This increase in the number of stations and the more timely receipt of data has allowed us and other seismological centers to locate earthquakes more rapidly and to locate many small earthquakes which were undetected in earlier years. The NEIC now locates about 20,000 earthquakes each year or approximately 50 per day. Also, because of the improvements in communications and the increased interest in the environment and natural disasters, the public now learns about more earthquakes.

According to long-term records (since about 1900), we expect about 17 major earthquakes (7.0 – 7.9) and one great earthquake (8.0 or above) in any given year.

A fast CME associated with an M5 flare from early September 6, 2011. The observation is from the LASCO C2 coronagraph aboard the SOHO spacecraft.

At 01:50 UT, sunspot group, AR11283, produced an M5 solar flare and CME (coronal mass ejection) from near the center of the solar disk. The CME  appears to be moving at an angle away from a path straight towards us. This means that while we may experience some impact its effects will be much less than if it was traveling straight towards us. Here is the event as observed by SDO/AIA in 2 wavelengths (131 and 211 Angstrom) along with observations of the CME in SOHO/LASCO C2 & C3 coronagraphs and the STEREO Cor2 coronagraphs from the Ahead and Behind spacecraft. It was a small to medium event and will probably have little impact on the Earth.

www.youtube.com/watch?v=XxhWKiF9ejE

This coronal mass ejection came from a filament eruption on the northeast disk of the Sun.

Well, it has been a fairly quiet couple of weeks since all the activity at the beginning of the month. Early in the morning of 28 August 2011, a small filament erupted with an associated B-class solar flare. Here is the event as observed by SDO/AIA in three wavelengths (171,193 and 211 Angstrom) along with SOHO/LASCO C2/C3 and the STEREO spacecraft. The event was on the northeast disk or upper right side of the Sun. It was a cool event but small and not Earth-directed. Enjoy!

www.youtube.com/watch?v=z47Q7GoWymU

credit: NASA, ESA, SDO, SOHO and STEREO

At about 8UT, August 9, 2011, sunspot group AR11263 produced the largest solar flare of the current solar cycle. The event also had associated with it a CME, coronal wave and particle event.

Sunspot group AR11263 is about to rotate out of view but before it goes, it produced a treat for us!! An X7 solar flare, coronal wave, coronal mass ejection (CME) and a well-connected proton event. This is the largest solar flare so far for solar cycle 24!! Check out this video for more information.

www.youtube.com/watch?v=C1mRkQ3t5Zk