A powerful X8.2 solar flare erupted from Region 2673, located just around the visible disk, at 16:06 UTC on September 10, 2017, causing R3 - Strong radio blackout and a rapid increase in relativistic proton levels. Within just 3 hours, solar radiation storm reached S3 - Strong levels (on a scale of 1 - 5).
The proton flux exceeded the S1 - Minor threshold at 16:45 UTC and continued to increase to a peak flux of 1 040 pfu at 18:45 UTC - R3 - Strong solar radiation storm threshold. Proton levels still remain at those levels at 07:49 UTC on September 11.
An enhancement in the energetic portion of the solar radiation spectrum may indicate increased biological risk to astronauts or passengers and crew in high latitude, high altitude flights. Additionally, energetic particles may represent an increased risk to all satellite systems susceptible to single event effects.
As reported by Dr. Tamitha Skov, a credentialed Space Meteorologist, due to the ongoing S3-level radiation storm, NASA model has an active alert for aircrew and prenatal [pregnant] passengers on transcontinental flights now. Check NAIRAS.
There are, on average, just ten S3 - Strong space radiation storms per one solar cycle (~11 years).
Potential impacts include:
- Radiation - Passengers and crew in high latitude, high altitude flights may experience increasing radiation exposures. Astronauts on EVA (extra-vehicular activity) are exposed to elevated radiation levels.
- Spacecraft - Single-event upsets to satellite operations, noise in imaging systems, and slight reduction of efficiency in solar panels are likely.
- Radio - Degraded or episodically blacked-out polar HF (high frequency) radio propagation.
Strong solar radiation storm hits ESA/NASA SOHO/LASCO C3 coronagraph
Read more: 4th X-class flare: X8.2 erupts from Region 2673, second strongest of the cycle (published September 10 and updated September 11)
What is solar radiation storm
Solar radiation storms occur when a large-scale magnetic eruption, often causing a coronal mass ejection and associated solar flare, accelerates charged particles in the solar atmosphere to very high velocities. The most important particles are protons which can get accelerated to 1/3 the speed of light or 100 000 km/s. At these speeds, the protons can traverse the 150 million km from Sun to Earth in just 30 minutes. When they reach Earth, the fast moving protons penetrate the magnetosphere that shields Earth from lower energy charged particles. Once inside the magnetosphere, the particles are guided down the magnetic field lines such that they penetrate the atmosphere near the north and south poles.
NOAA categorizes Solar Radiation Storms using the NOAA Space Weather Scale on a scale from S1 - S5. The scale is based on measurements of energetic protons taken by the GOES satellite in geosynchronous orbit. The start of a Solar Radiation Storm is defined as the time when the flux of protons at energies ≥ 10 MeV equals or exceeds 10 proton flux units (1 pfu = 1 particle*cm-2*s-1*ster-1). The end of a Solar Radiation Storm is defined as the last time when the flux of ≥ 10 MeV protons is measured at or above 10 pfu. This definition allows multiple injections from flares and interplanetary shocks to be encompassed by a single Solar Radiation Storm. A Solar Radiation Storm can persist for time periods ranging from hours to days.
Solar Radiation Storms cause several impacts near Earth. When energetic protons collide with satellites or humans in space, they can penetrate deep into the object that they collide with and cause damage to electronic circuits or biological DNA. During Solar Radiation Storms at the S2 or higher level passengers and crew in high flying aircraft at high latitudes may be exposed to radiation risk. When the energetic protons collide with the atmosphere, they ionize the atoms and molecules thus creating free electrons. These electrons create a layer near the bottom of the ionosphere that can absorb High Frequency (HF) radio waves making radio communication difficult or impossible. (NOAA)
Featured image: Strong radiation storm hiting ESA/NASA SOHO/LASCO C3 coronagraph at 01:34 UTC on September 11, 2017. Credit: ESA/NASA SOHO/LASCO C3