STORM SIGNALS
From Satellites: RHESSI Light Curves
Live Data
RHESSI Light curves
A complete list of real-time data links is located in the Space Weather Resources section.
The RHESSI satellite uses an instrument that measures high-energy x-ray emissions at many different energies. RHESSI Light Curve data can be used to identify solar flares and to compare with GOES and WIND WAVES data. RHESSI Light Curve data are near real-time with only a few hours processing time.
When you click on the RHESSI Light Curve Link you will see the following image.
Navigation: When the page first opens it will show a recent time interval, but not necessarily the most recent data available.
Click on the year and month you want to examine.
Click on the day of the month in the column numbered
1 - 30 or 31.
The arrows at the top allow you to choose previous time period (back arrow) or the next time period (forward arrow). The outside arrows change the time period by one day. The inner arrows change time by one orbit (a few hours).
Click on the arrows until you get the time period you
want. (Remember, the time is given in Universal Time (UT)
Leave the Rates setting at 'Summary, corrected'.
Interpreting the Light Curve:
The plot shows the number of photons of x-ray light arriving at the detector per second. There are nine different energy ranges displayed. The time interval begins and ends at orbit midnight (when the spacecraft is on the opposite side of Earth from the Sun).
There is an Explanation of the plots linked at the bottom of each Quick Plots page. It is recommended that you read this explanation, however, a few highlights here will help you to interpret the data.
The colored bars along the top give important information.
The red F and red bar: This means there was a flare. The bar shows how long the flare lasted. The scientists have interpreted the data for you! This helps you to ignore some of the variations in the light curves that are not solar flares, but are caused by several different phenomena.
TEACHER'S NOTE
There are several conditions that can lead to misleading results in these plots. The scientists and engineers have identified these artifacts and described them and the effect on the data. You can find these at Artifacts in RHESSI Light Curves
The cyan N and cyan bar: The spacecraft is in Earth's shadow and cannot see the Sun. Unlike spacecraft like SOHO, which is located at the gravitational balance point between Earth and Sun and continuously observes the Sun, RHESSI orbits Earth and during roughly half of its orbit it is in Earth's shadow and cannot see the Sun.
The orange S and orange bar: The spacecraft is passing through the South Atlantic Anomaly. The instruments on RHESSI are turned off to protect them from contamination and damage from high doses of radiation in this region over the South Atlantic.
TEACHER'S NOTE
The South Atlantic Anomaly is a very interesting result of the lack of alignment of Earth's magnetic and spin axis. The magnetic poles are not located at the geographic poles and a line connecting the two magnetic poles does not pass directly through the center of Earth. This means that when you imagine the bar-magnet-like magnetic field surrounding Earth, it does not surround it symmetrically.
In general, a field line on one side of Earth is not at the same distance from the surface as the equivalent line on the other side of Earth. One is closer. At two different distances from Earth, are belts of fast moving particles (electrons and protons) that are trapped inside the magnetic field. These belts are called the Van Allen radiation belts. Since the belts are formed by the magnetic field they also are symmetric around Earth. Imagine a belt fastened in a loop and ball placed in the middle. If you put the ball slightly off-center inside the belt, the one part of the belt will be closer to one side of the ball than the other. The location where the inner Van Allen radiation belt comes closest to Earth is over the South Atlantic Ocean. When spacecraft fly through this region they experience high doses of radiation compared to other locations at the same altitude.
- NASA Official: Dr. James Thieman
- Project Manager: Don Robinson-Boonstra
- Website Manager: Bryan Stephenson