September 2017 Was 🔥 on the Sun

The Sun started September 2017 with flair, emitting 31 sizable solar flares and releasing several powerful coronal mass ejections, or CMEs, between Sept. 6-10.

Solar flares are powerful bursts of radiation. Harmful radiation from a flare cannot pass through Earth’s atmosphere to physically affect humans on the ground, however — when intense enough — they can disturb the atmosphere in the layer where GPS and communications signals travel. 

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CMEs are massive clouds of solar material and magnetic fields that erupt from the Sun at incredible speeds. Depending on the direction they’re traveling in, CMEs can spark powerful geomagnetic storms in Earth’s magnetic field.

As always, we and our partners had many missions observing the Sun from both Earth and space, enabling scientists to study these events from multiple perspectives. With this integrated picture of solar activity, scientists can better track the evolution of solar eruptions and work toward improving our understanding of space weather.

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The National Oceanic and Atmospheric Administration (NOAA)’s Geostationary Operational Environmental Satellite-16, or GOES-16, watches the Sun’s upper atmosphere — called the corona — at six different wavelengths, allowing it to observe a wide range of solar phenomena. GOES-16 caught this footage of an X9.3 flare on Sept. 6, 2017. 

This was the most intense flare recorded during the current 11-year solar cycle. X-class denotes the most intense flares, while the number provides more information about its strength. An X2 is twice as intense as an X1, an X3 is three times as intense, and so on. GOES also detected solar energetic particles associated with this activity.

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Our Solar Dynamics Observatory captured these images of X2.2 and X9.3 flares on Sept. 6, 2017, in a wavelength of extreme ultraviolet light that shows solar material heated to over one million degrees Fahrenheit.

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JAXA/NASA’s Hinode caught this video of an X8.2 flare on Sept. 10, 2017, the second largest flare of this solar cycle, with its X-ray Telescope. The instrument captures X-ray images of the corona to help scientists link changes in the Sun’s magnetic field to explosive solar events like this flare.

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Key instruments aboard our Solar and Terrestrial Relations Observatory, or STEREO, include a pair of coronagraphs — instruments that use a metal disk called an occulting disk to study the corona. The occulting disk blocks the Sun’s bright light, making it possible to discern the detailed features of the Sun’s outer atmosphere and track coronal mass ejections as they erupt from the Sun.

On Sept. 9, 2017, STEREO watched a CME erupt from the Sun. The next day, STEREO observed an even bigger CME. The Sept. 10 CME traveled away from the Sun at calculated speeds as high as 7 million mph, and was one of the fastest CMEs ever recorded. The CME was not Earth-directed: It side-swiped Earth’s magnetic field, and therefore did not cause significant geomagnetic activity. Mercury is in view as the bright white dot moving leftwards in the frame.

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Like STEREO, ESA/NASA’s Solar and Heliospheric Observatory, or SOHO, uses a coronagraph to track solar storms. SOHO also observed the CMEs that occurred during Sept. 9-10, 2017; multiple views provide more information for space weather models. As the CME expands beyond SOHO’s field of view, a flurry of what looks like snow floods the frame. These are high-energy particles flung out ahead of the CME at near-light speeds that struck SOHO’s imager.

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Our Interface Region Imaging Spectrometer, or IRIS, captured this video on Sept. 10, 2017, showing jets of solar material swimming down toward the Sun’s surface. These structures are sometimes observed in the corona during solar flares, and this particular set was associated with the X8.2 flare of the same day.  

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Our Solar Radiation and Climate Experiment, or SORCE, collected the above data on total solar irradiance, the total amount of the Sun’s radiant energy, throughout Sept. 2017. While the Sun produced high levels of extreme ultraviolet light, SORCE actually detected a dip in total irradiance during the month’s intense solar activity. 

A possible explanation for this observation is that over the active regions — where solar flares originate — the darkening effect of sunspots is greater than the brightening effect of the flare’s extreme ultraviolet emissions. As a result, the total solar irradiance suddenly dropped during the flare events. 

Scientists gather long-term solar irradiance data in order to understand not only our dynamic star, but also its relationship to Earth’s environment and climate. We are ready to launch the Total Spectral solar Irradiance Sensor-1, or TSIS-1, this December to continue making total solar irradiance measurements.

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The intense solar activity also sparked global aurora on Mars more than 25 times brighter than any previously seen by NASA’s Mars Atmosphere and Volatile Evolution, or MAVEN, mission. MAVEN studies the Martian atmosphere’s interaction with the solar wind, the constant flow of charged particles from the Sun. These images from MAVEN’s Imaging Ultraviolet Spectrograph show the appearance of bright aurora on Mars during the September solar storm. The purple-white colors show the intensity of ultraviolet light on Mars’ night side before (left) and during (right) the event.

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GOES images are courtesy of NOAA. Hinode images are courtesy of JAXA and NASA. SOHO images are courtesy of ESA and NASA. 

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