A "Textbook" Flare

Click on the image for an annotated version

Movies (JavaScript): Individually scaled frames, Uniformly scaled frames

Caption: During an observation sequence supporting the RHESSI mission, the Coronal Diagnostic Spectrometer (CDS) caught a textbook example of a low-level flare (classified as a C3.1). The images in the frame above show active region AR 9878 as it appeared in five different emission lines during the initial, impulsive phase of the flare. The emission line images are ordered by their so-called "line formation temperature", the typical temperature of matter emitting light in these specific wavelengths. From top left they are: He I (neutral helium: 30,000K), O V (four times ionized oxygen: 230,000K), Mg X (nine times ionized magnesium: 1,100,000K), Fe XVI (fifteen times ionized iron: 2,700,000K), and Fe XIX (twenty times ionized iron: 7,800,000K).

The movies show the whole observation sequence, with two different color scalings: One with each frame and emission line scaled to bring out the most details, and one with a uniform scaling for each line over the whole observation series (showing the true dynamic range of the observation series).

The frame above is particularly interesting because it shows the footpoints of a magnetic loop brighten up as the flare goes off, at all temperatures. However, only in the hottest line does one see any emission from the middle of the loop - from one "hot spot" in particular. The loop is "lighting up" in the cooler lines in subsequent frames.

On a side note, the CDS spectrometer may now boast about being the source of "perhaps the biggest EUV spectrum in the world": A wall in a swimming hall has been decorated with a 20 meter long mosaic of the CDS spectrum, using over 50,000 Italian glass tiles:

©CLRC-02RC1164

The original quiet Sun spectrum as recorded by CDS is shown below, highlighting the number of spectral lines that can be observed simultaneously by the CDS instrument:

Click on the image for an annotated version

Taken: 14:50-21:20UT, March 26, 2002
Picture credits: SOHO/CDS (ESA & NASA)