# The Sun and Space Weather
## 7 Space Weather Events and Spacecraft Anomalies  
SEPs are known to impact satellites in Earth's orbit. For example, when satellite solar panels are directly exposed to energetic protons, the current generated by the panels decreases significantly and permanently. [PERSON] and [PERSON] [160] reported that two large SEP events, which occurred on 29 September 1989 and October 19, decreased the expected current from GOES-7 solar arrays by \(\sim\)5-10%. [PERSON] et al. [161] performed a statistical analysis of a large number of spacecraft anomalies in different Earth orbits. They found \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**CME Date** & **Time (UT)** & **Speed (km/s)** & **Location** & **Ip (GOES)** & **Ip (STB)** \\ \hline
28 December 2001 & 20:30 & 2216 & S26E90 & 76 & — \\
8 January 2002 & 17:54 & 1794 & \(>\)NE90 & 28 & — \\
27 July 2005 & 04:54 & 1787 & N11E90 & 41 & — \\
22 September 2011 & 10:48 & 1905 & N09E89 & 35 & 5000 \\
21 June 2013 & 03:12 & 1900 & S16E73 & 14 & 100 \\
25 Febraury 2014 & 01:25 & 2147 & S12E82 & 24 & 300 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: CME speeds and SEP intensities of east-limb events observed by GOES and STB. Figure 16: The 2002 April 21 eruption: (**a**) GOES soft X-ray flare, (**b**) the flare imaged by SOHO/EIT, and (**c**) the CME imaged by SOHO/LASCO. The dots and streaks in the CME image are due to energetic particles from the CME impacting the SOHO/LASCO detector and are referred to as a “snowstorm”. that spacecraft in high-altitude, high-inclination (HH) orbits exhibited higher frequencies of spacecraft anomalies compared to those at lower altitudes and inclinations (LL, LH), as summarized in Figure 17. We see that the anomaly frequency is the highest for spacecraft in high-altitude, high-inclination (HH) orbits. These are the orbits in which most of the GNSS satellites are located. The anomaly frequency rapidly increases with proton flux. For example, for HH orbits, the anomaly frequency increases by an order of magnitude when the proton flux increases from 100 to 1000 pfu. The probability of an anomaly for HH orbit is significantly higher for higher proton flux and proton energy. Finally, the anomaly frequency peaks typically 4-5 days after the onset of the proton event. Interestingly, the spacecraft anomalies also peak following geomagnetic storms. Figure 18 shows the anomaly frequency as a function time starting from the time of storm sudden commencement (SSC). For satellites in high latitudes and low latitudes, the anomaly frequency peaks about three and five days after SSC, respectively. The anomaly peaks roughly coincide with the time of peak relativistic electron flux following the initiation of a geomagnetic storm. The relativistic electron flux peaks earlier at lower energies because of the progressive energization of electrons by low-frequency waves generated by low-energy particles injected into the magnetosphere during storm-time substorms (see e.g., [162]). The relativistic electron flux is enhanced both during CME and CIR storms, although CIR storms elevate the flux to much higher levels than the CME storms do [163]. The relativistic electrons can be as harmful as the SEPs in causing satellite anomalies [164]. The spacecraft anomalies occur because of the interaction between spacecraft and their hazardous environment. The resulting impact depends on the energy and the type of particles involved [166]. Table 3 lists the impact on spacecraft by electrons, protons, and heavier ions of various energies and sources. Figure 17: (**a**) The normalized frequency of spacecraft anomalies (averaged over the first 2 days of proton enhancements) as a function of maximal proton flux at energies >10 MeV from IMP8 for various Earth orbits: high altitude with high inclination (HH, red), high altitude with low inclination (HL, green), and low altitude with high inclination (LH, black). (**b**) The probability of anomaly as a function of proton flux in two different energy channels (>10 MeV in black and >60 MeV in red).