Space Weather

Space Weather

Space weather describes changing environmental conditions in near-Earth space. Magnetic fields, radiation, particles and matter, which have been ejected from the Sun, can interact with the Earth’s upper atmosphere and surrounding magnetic field to produce a  variety of effects.

Image courtesy of NASA/SDO and the AIA, EVE, and HMI science teams

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Aurora forecasts

Northern Hemisphere

The forecast for enhancement of the auroral oval is low confidence in timing and phasing, given up to three Coronal Mass Ejections (CMEs) in the forecast. Confidence is however higher for G1 being the maximum attained geomagnetic activity, which typically would manifest over northern Scotland and similar geomagnetic latitudes.

In the absence of these CME effects, Quiet ambient activity should gradually give way to more often unsettled periods given the more reliable coronal hole high speed stream(s) onset(s). This would manifest at high latitudes only (far northern Europe).

Southern Hemisphere

The forecast for enhancement of the auroral oval is low confidence in timing and phasing, given up to three Coronal Mass Ejections (CMEs) in the forecast. Confidence is however higher for G1 being the maximum attained geomagnetic activity, which typically would manifest over the Antarctic peninsula and similar geomagnetic latitudes.

In the absence of these CME effects, Quiet ambient activity should gradually give way to more often unsettled periods given the more reliable coronal hole high speed stream(s) onset(s). This would manifest at high latitudes only.

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Forecast overview

Space Weather Forecast Headline: Slight daily chance of G1/Minor Geomagnetic Storms from Coronal Mass Ejections (CMEs) throughout.

Analysis of Space Weather Activity over past 24 hours

Solar Activity: Solar activity fell to become very low in the past 24 hours, with no significant X-ray flares recorded. The number of sunspots on the facing side of the sun also fell, with just two magnetically unipolar groups now surviving. Two recent large sunspot groups, including that responsible for the recent R2 and S1 alerts, now lie narrowly over the western solar horizon - with small and ever-decreasing chances of producing further X-ray flares or solar radiation storms large enough to be detected at Earth. Finally, a further small and inactive unipolar sunspot became indistinct near the southwest solar horizon.

At 21/0900UTC, a large 'filament' (arc of plasma) disappeared from immediately north of the easternmost surviving sunspot, with this event visible on ground-based near infra-red imagery for the period (e.g. from Udaipur observatory, India). This was tied to a long-lasting but sub-common class X-ray flare. A Coronal Mass Ejection (CME) was visible in available satellite imagery, however this is not considered Earth-directed, with no other events of note observed.

Having being emitted prior to this this 24-hour period, there are numerous potential CME glances and near misses in the forecast - see the 'Solar Wind / Geomagnetic Activity' section for detail.

Solar Wind / Geomagnetic Activity: The solar wind was suggestive of an ongoing exit from a fast regime from a 'coronal hole' near the western solar horizon.

The solar wind speed fell in the 24 hours within slightly elevated levels, while the number of particles in the solar wind was unremarkable and showed a slight downward trend. The magnetic field tied to these particles also showed a slight decay - within background levels. The net effect of the above solar wind measures was for provisionally quiet geomagnetic activity throughout - at the very bottom of the measurement scale and well below G1.

Energetic Particles / Solar Radiation: The detected solar radiation storm showed a declining response from S1 to start the period, having initially being reached in the wake of the middle-ranking Moderate class X-ray flare that preceded this 24-hour period. This measurement of solar radiation accordingly crossed below the S1 threshold from 20/2000UTC. The 'harder' solar radiation response (due to more massive protons) also fell, starting the period narrowly below the alert threshold and subsequently falling.

Four-Day Space Weather Forecast Summary

Solar Activity: There continues to be a decreasing slight chance of further isolated Moderate-class X-ray flares given two large sunspots' proximity to the western solar horizon. With an otherwise simple (in terms of sunspots) Earth-facing side of the sun and no returning regions due, very low solar activity is expected into the UTC weekend.

Solar Wind / Geomagnetic Activity: There are three potential CME arrivals through the period. Firstly, there is a chance of a glancing impact either late today (Friday 21 January) or early Saturday from the CME from the Moderate-class X-ray flare on 19 January. Secondly, a CME leaving the southwest of the sun (from an ejected arc of plasma (filament eruption)) on 20 January may brush Earth with limited impacts on day 4 (Monday 24 January). Thirdly, a further CME which occurred on 19 January has the potential to arrive day 3 (Sunday 23 January), with confidence slightly higher for some limited impacts at Earth for this feature.

In addition to the complicated CME forecast, a fast solar wind regime may otherwise re-establish as a pair of 'coronal holes' may feature at Earth from later in the UTC weekend.

The resultant forecast is very low confidence in timing and phasing of Minor Geomagnetic Storm G1 risk, but higher for this being the maximum attained geomagnetic activity. In the absence of especially low confidence CME effects, the trend should otherwise be for quiet ambient activity gradually increasing - given the more reliable fast wind high speeds stream(s) onset(s). 

Energetic Particles / Solar Radiation: Solar radiation storms are forecast to slowly decrease back to Background levels of risk in the first half of the forecast period. The chances of further such enhancements should now gradually fall with time from a peak early slight chance - the result of large sunspot regions lying narrowly over the western solar horizon but rotating away with time.

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Solar imagery

SDO AIA-193

This channel highlights the outer atmosphere of the Sun - called the corona - as well as hot flare plasma. Hot active regions, solar flares, and coronal mass ejections will appear bright here. The dark areas - called coronal holes - are places where very little radiation is emitted, yet are the main source of solar wind particles.

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SDO AIA-304

This channel is especially good at showing areas where cooler dense plumes of plasma (filaments and prominences) are located above the visible surface of the Sun. Many of these features either can't be seen or appear as dark lines in the other channels. The bright areas show places where the plasma has a high density.

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