May 14, 2024
A powerful solar storm impacted Earth in early May 2024, triggered by the highly active region AR13664. This region unleashed a series of X-class flares and coronal mass ejections (CMEs) directed at Earth. The resulting geomagnetic storm was the most intense since 2003 (Dst index -412 nT), causing disruptions to communication and GPS systems.There have been many M-class and C-class flares as well. Many of these flares were accompanied with halo CMEs (CMEs that are the one which are directed towards Earth) with high energy particles which are behind the geomagnetic storms observed on early hours of 11 May 2024. Geomagnetic storm index (Kp) touched 9 (which is maximum) and Very strong X-class flare (X 5.8) was recorded.Solar flares are bursts of energy triggered by magnetic reconnection, classified by letter (B-X) with each letter signifying a tenfold increase in power. X-class flares are the most powerful (peak flux range > 10−4 Wm-2), which can trigger major disruptions. The next lower level of flares, the M class, represents the peak flux range of 10−5 – 10−4 Wm-2.
This is the biggest Geomagnetic storm since 2003 in terms of its strength, as the flaring region on the Sun was as big as the historically important Carrington event that took place in 1859. Multiple X-class flares and CMEs have hit the earth in the past few days. This had severe effects over high latitudes where trans-polar flights are already being reported to get diverted. More events are expected in the next few days. Indian sector got less affected as the main hit of the storm happened in the early morning of 11th May, when ionosphere has not developed fully. Also, being at lower latitudes, widespread outages haven't been reported in India.Ionosphere was very turbulent over the Pacific and American sectors.
Observations from Ground
The main punch of this event so far arrived in the early morning hours of 11 May in India, when Ionosphere was not fully developed. The GNSS network observations at the National Atmospheric Research Laboratory (NARL, at Gadanki, Andhra Pradesh- with coordinates13.4593° N, 79.1684° E) show decrease of the Total Electron Content (TEC) by more than 50% from 10 May midnight to 11 May morning. On 11 May daytime TEC was high by about 10% with large variations indicating disturbed ionosphere. In the evening TEC is nearly 30% more. No L band scintillation has been observed. Radar observations showed no bubble, consistent with TEC and scintillation observed by GNSS receivers.
While this was the observation from Gadanki, the observations by the Thumba (coordinates 8.5310° N, 76.8750° E) node of the INSWIM (Indian Network for Space Weather Impact Monitoring) network was more dramatic. This is expected, as the ionospheric ring current, which is enhanced during geomagnetic storms, passes over the sky of Thumba.In response to the geomagnetic storm on May 11, 2024 a sharp enhancement in the TEC values was observed at Trivandrum post 8 UT and by 10 UT, it lead to over 100 % increase compared to the control day on 09/10 May. About 80 TECu (1 Total Electron Content unit of TECu means 1016 electrons per meter square in a column integrated sense) plasma at 09 AM IST over Trivandrum. It's huge in comparison with the typical value of TEC at the same local time, which is ~10-20 TECu.
Observations from Space
ISRO has mobilised all its observation platforms and systems to record the signatures of this event. Both Aditya-L1 and Chandrayaan-2 have made observations and signatures have been analysed.
Observations by Aditya-L1
Meanwhile, the ASPEX payload on-board Aditya -L1 is showing high speed solar wind, high temperature solar wind plasma and energetic ion flux till now.ASPEX comprises two subsystem instruments – the Solar wind Ion Spectrometer (SWIS) and STEPS (SupraThermal and Energetic Particle Spectrometer). The THA-1 (Top Hat Analyser-1) of SWIS works in species differentiated mode and measures the He++ (alpha particles) and H+ ions (protons) separately in 2π radians in the ecliptic plane, while THA-2 (Top Hat Analyser-2) of SWIS works in the species integrated mode in 2π radians across the ecliptic plane. Figure 1 shows the energy histogram for the SWIS sensor in ASPEX., which captures the signature of the solar wind. SWIS has captured the enhancement of the alpha particle and proton flux of the solar wind as a signature of this solar eruptive event.
Figure 1: Proton (lower) and alpha (upper) lines are seen from the THA-1 and 2 SWIS observations. The prominent change in the flux is noticed as the signature of this solar eruptive event. The upper and lower panels represent the observations from THA-1 and THA-2 of the SWIS. The colour bar represents the raw counts, in log scale.
Figure 2 presents the observations from STEPS. This measures the flux of the solar wind ions at seven energy ranges. A steady rise in the energetic ion fluxes during the event has been noticed.
Figure 2: Rise in the ion flux as observed by the STEPS. Each of the curve corresponds to specific energy bands.
The X-ray payloads on-board Aditya-L1 (SoLEXS and HEL1OS) have observed the multiple X- and M-class flares from these regions during the last few days while the in-situ magnetometer (MAG) payload has also observed the events as it passed by the L1 point. The observations made by SoLEXS, HEL1OS and MAG payloads are presented in Figures 3, 4 and 5 respectively.
Figure 3:LIghtcurve from SoLEXS. It has captured the signatures of the X-class flares in the soft X-Ray regime.
Figure 4: Lightcure from HEL1OS. It has also captured X class of flares, in the hard X-Ray regime.
Figure 5: The measurements with the MAG payload has captured the perturbations in the Interplanetary Magnetic Field (IMF) caused by the solar eruptions.
Observations by Chandrayaan-2
While the Aditya-L1 observes the Sun from the first Sun-Earth Lagrange point, the Chandrayaan-2 orbiter has also captured the signatures of these solar eruptive events from the lunar polar orbit. XSM has observed many interesting phenomena associated with this geomagnetic storm. Figure 6 shows the solar X-ray flux in the 1 – 8 A range (the same range used by NOAA GOES). The large solar flares (> M5 class), manifested as spikes, are autonomously identified by the onboard logic of XSM, when the internal mechanism was activated to reduce the incident X-ray flux by bringing a filter in front of the detector, so as to prevent its saturation.
While the XSM primarily monitors solar X-rays, it has also provided information about the local high energy particle environment by means of counting the events when the upper level discriminator (ULD) threshold is crossed. The ULD event light curve over the past five days, shown in Figure 7, clearly shows the enhancement of the local charge particle concentration from 9th May onwards. The dips observed in the XSM ULD light curve are due to the shadow effect arising from orbit of the spacecraft around the Moon.
Figure 6: Chandrayaan-2 XSM light curve of 1-8 angstrom X-ray flux. The gaps in the light curve are due to the Sun going out of the XSM field of view as the Chandrayaan-2 spacecraft orbits around the Moon. For more details about the observational aspects of XSM, please check the XSM website at https://www.prl.res.in/ch2xsm/
Figure 7: Variability of high-energy particles in the lunar orbit from ULD events observed by Chandrayaan-2 XSM
On the Spacecraft Health
The Master Control Facility (MCF) team in ISROwas on alert and watchful of any Geomagnetic activity experienced by geo spacecrafts. With respect to disturbances on spacecrafts, the magnetic torquer duty cycle changes due to increased accumulation of disturbances resulting in frequent momentum dumps.
Momentum Wheel speed deviations were observed along with MTC current saturation in few spacecrafts. Spacecrafts with one-sided panel had predominant signature variations which required frequent momentum dumping. Otherwise, overall operations were normal. No single event upsets were seen.Star Sensor (SS-2) in INSAT-3DS and Star Sensor (SS-3) in INSAT-3DR were turned off as per Mission.
Other than this there has not been any major upsets or anomaly observed in any of the 30 GEO spacecrafts so far.
None of the Earth Observation Satellites of ISRO which were visible from ISRO’s ground stations had any upsets or latch-ups.
During solar events like this, the energy released from the Sun heats and expands the upper atmosphere. This increased atmospheric density at satellite altitudes creates more drag on satellites, causing them to lose altitude gradually. This effect is most pronounced for satellites in low-Earth orbit. A few cases of satellite orbit decay have also been noticed (Fig 8). Orbit decay of EOS-07 at ~430 km with nearly 153 kg mass is nominally 300 meters and on 11 May the decay observed 600meters. Orbit decay of Cartosat-2F at 505 km with mass of nearly 688 kg is normally 35 to 40 meters and on 11 may the decay observed was 180 meters (refer Fig. 9). In general, the orbit decay of all satellites increased by 5 to 6 times compared to nominal valueon 11 May 2024.
Figure 8: Orbit decay for various satellites on May 10, 2024
Figure 9: Table presenting the orbit decay due to atmospheric drag for the LEO satellites on May 11, 2024
The ISRO Navigation Centre has not noticed any significant degradation in the NaVIC service metrices till now, indicating no or negligible impact from the geomagnetic storm.