RHESSI in Cycle 24
| RHESSI in Cycle 24 | |
|---|---|
| Number: | 108 |
| 1st Author: | Säm Krucker |
| 2nd Author: | Hugh Hudson |
| Published: | 17 August 2009 |
| Next Nugget: | NUGGET 109 |
| Previous Nugget: | CMEless Flares |
Introduction
In anticipation of Solar Cycle 24 and the hoped-for huge flares it would produce, the RHESSI germanium detectors were annealed in late 2007. This process removes radiation damage caused by the continual exposure of the detectors to the Earth's radiation belts. It is a bit of a race against time for RHESSI, because we think that only a limited number of anneals will be possible; eventually they may poison the segmentation of the detectors and effectively eliminate their gamma-ray response. But, so far so good, as shown in this Nugget with a new-cycle flare. For readers puzzled by this, since in recent Nuggets (April and July 2009) we have worried about the great delay in Cycle 24's onset. Nonetheless at the time of writing there have already been some new-cycle spots and flares, although it is still the case that activity has not turned up as expected. We are still worried!
The flare we have imaged
This was a GOES C1 event on July 6, 2009. Its active region was at S25, a latitude where new-cycle spots tend to appear, and had the new-cycle polarity. So, no matter how feeble this cycle may turn out to be, we have tiny flares and may hope for more energetic ones that can be observed by RHESSI at all energies, ie up into the gamma-ray range.