Indian satellites did not suffer any major outages due to the multiple powerful earth-bound solar storms recently, the Indian Space Research Organisation (ISRO) has said. On May 10 and 11, intense solar storms triggered by the highly active region AR13664 on the sun were directed towards the earth. At least four 'X' class (highest intensity) and multiple 'M' class (moderate intensity) solar flares were set off from this active region. These were the strongest solar flares to reach the earth since November 2003, and the sun's flaring region resembled the historically important Carrington event of 1859. The storm intensities were so high that they triggered a range of aurorae over the high-altitude regions in the northern hemisphere. Some aurorae were also captured from lower-latitude regions like Ladakh in India. Both ISRO's ground- and space-based observatories were geared up to capture the solar event, and they successfully recorded the multiple disturbances caused by the Coronal Mass Ejection (CME) and intense solar flares. "The Indian sector remained less affected by the solar storm event of May 11. Being in lower latitudes, there were no widespread outages in India. The Ionosphere was more turbulent over the Pacific and American than the Indian sector, where it was not fully developed on May 11," the ISRO said on Tuesday. Even though the solar flares reported on May 10 and 11 were high intensity, the ISRO said that operations of all its 30 spacecraft in the geostationary orbit have remained unaffected. The Star Sensor onboard INSAT-3DS and INSAT-3DR, used by the India Meteorological Department (IMD), was temporarily switched off as a precautionary measure. However, some of its satellites orbiting along the Low Earth Orbit (LEO) suffered drag, a phenomenon manifested by excessive heating of the earth's atmosphere due to such high solar events. The 153 kg satellite EOS-07 (at 430 km altitude) suffered an orbital decay of 300 metres and 600 metres on May 10 and May 11, respectively. Cartosat-F, weighing 688kg, experienced an orbital decay up to 180 metres against a normal of 35 - 40 metres during this period of high solar activity. At least nine LEO satellites experienced orbital decay on May 11, the ISRO data stated. These include Cartosat-2s, Risat-2B series, Cartosat-2B, X01, R2A and Micro-2B whose orbital decay ranged between 50 -600 metres from normal. "The orbit decay of all satellites increased by 5 to 6 times than nominal value on May 11," the ISRO said. The Solar Low Energy X-ray Spectrometer (SoLEXS) and High Energy L1 Orbiting X-ray Spectrometer (HEL1OS) onboard Aditya L1 - the India Space Research Organisation's latest and first solar mission from space - observed multiple X and M-class solar flares. The in-situ measuring magnetometer, too, captured the sun's enhanced activities as it passed through the Lagrange point 1 (L1), where Aditya was successfully inserted earlier this year. The ISRO on Tuesday said that since May 10, ASPEX, another payload onboard Aditya L1, has been showing solar winds with above-normal speeds and temperatures in addition to energetic ion flux. One of its subsystems, the Solar Wind Ion Spectrometer (SWIS), managed to capture the enhancement of particle and proton flux of the solar wind, confirming its eruptive nature. Chandrayaan-2, which performed observations from the lunar polar orbit, captured an interesting phenomenon about the geomagnetic storm. The onboard Solar X-Ray Monitor (XSM) provided vital information about the local high-energy particle environment, which remained enhanced since May 9. Many of these flares were accompanied by halo CMEs and high-energy particles that follow the geomagnetic storm. The early hours observations on May 11 suggested that the Geomagnetic Storm Index (Kp) touched 9, which is considered the maximum.
