For event E1, early on February 25, 2014, around 00:50 UTC, active region AR1990 (near equatorial, eastern solar limb) erupted, producing an X4.9 class flare, a moderate SEP event by midday, and a CME whose ejecta delivered a glancing blow 2.5 days later to geospace in the afternoon of February 27. Now we summarize the activities for our three events. This three-column figure layout is repeated throughout the chapter. The dashed blue and gray lines demark the flux which needed to be classified as X-class and M-class events (10 − 4 and 10 − 5 watts/m 2). The vertical line (cyan) indicates the XRS observation at the time that the SXI image was generated.
#Sun flare exposure x series
The XRS time series is for the 0.1–0.8 band (are in watts/m 2) with all three events spanning 3 days (February 24–26, 2014 March 16–18, 2015 June 21–23, 2015). SXI images were taken using the PTHN filter (0.6–6.5 nm), an exposure time of 0.4 s and are in uncalibrated units of (digital number (DN/s)). GOES SXI solar X-ray (top) and XRS solar X-ray observations (bottom) for events E1 (left), E2 (middle) and E3 (right).
For details on the XRS instrument design, modes of operation and derived products, see Bornmann et al. Bands covered by the XRS instrument have been observed by NOAA satellites since 1974. For details on the SXI instrument design, modes of operation, and derived products, see Bornmann et al. An SXI instrument has been included on GOES spacecraft since GOES-12 (first operational in January 22, 2003). In modern solar wind terminology, an SIR which persists for more than one solar rotation is known as a co-rotating interaction region (CIR).
These are representative of coronal holes, which are source regions for higher solar wind velocity, and in the downstream interplanetary medium create stream interaction regions (SIRs), which can produce roughly 27-day repeat frequency geomagnetic storms at geospace. Darker high-latitude patches are seen in events E2 and E3. SEPs are generated by the two primary acceleration mechanisms: flare, through magnetic reconnection, and shock, via CMEs propagating through the interplanetary medium ( Gopalswamy et al., 2012). CMEs are explosive events that may emanate from the same active region as solar flares or eruptive filament/prominence structures. It's worth noting that solar active regions aren't the only source of CMEs, and hence SEPs. Common to all three events are the several bright, active regions in the equatorial and mid-latitudes, which are sources of increased X-ray flux, and potential flares, SEP, and CME events. Events one (E1), two (E2), and three (E3) are shown in the left, center, and middle columns, respectively. The images shown here used the Thin Polymide filter (PTHN, 0.6–6.5 nm) with a 0.4 s integration time, which is particularly useful for imaging coronal holes (see below). SXI images the Sun over a broad range of wavelengths from soft X-ray to extreme ultraviolet. Observations of the solar corona in the X-ray band from the GOES-15 Solar X-ray imager (SXI) (top row) and X-ray sensor (XRS) (bottom row) are shown in Fig. Here we summarize solar observations from NOAA's GOES spacecraft.