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 high speed stream from coronal hole 44 is expected to gradually wane through the period, with the auroral oval becoming less pronounced and limited to high latitudes. On Thursday 20 January, there is a slight chance of a further enhancement from a CME that left the sun on 16 January, although this aspect is low confidence.

Southern Hemisphere

The high speed stream from coronal hole 44 is expected to gradually wane through the period, with the auroral oval becoming less pronounced and limited to high latitudes. On Thursday 20 January, there is a slight chance of a further enhancement from a CME that left the sun on 16 January, although this aspect is low confidence.

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Forecast overview

Space Weather Forecast Headline: Slight Chance of Minor Geomagnetic Storm G1 Thursday 20 January from re-analysed 16 January CME. Chance of isolated Moderate-class X-ray flares (R1/R2 radio blackouts) throughout.

Analysis of Space Weather Activity over past 24 hours

Solar Activity: Solar activity has been low through the UTC day of Monday 17 January. X-ray activity saw a double-peak common class flare from one of the most magnetically complex sunspot regions on the sun at 17/1414UTC, potentially triggering an adjacent 'filament lift off' (a possible Coronal Mass Ejection (CME)) peaking at at 17/1516UTC. The CME from this latter event was clearly visible in satellite imagery to end the UTC day, angled above and ahead of the Earth in its orbit (to no anticipated effect). This was the only CME event of note visible in the period.

There are now six sunspot regions on the sun, with a small unipolar group having faded from view near the southwestern solar horizon, while a further three active regions saw out the period as stable unipolar groups. Of the (more complex and liable to flare) bipolar regions, two showed overall decay and no significant flares. This left the northwesternmost as the most noteworthy and active spot, with some proliferation visible in its intermediate spots, although again, overall areal decay was observed.

The CME from 14 January is now considered to have passed the radius of the Earth's orbit to no effect at Earth and has been removed from the forecast. The common-class flare from one of the larger sunspots on 16 January produced a CME directed mainly to the northwest of the Earth in the plane of its orbit. This has been re-analysed and may pass Earth as a glancing blow on Thursday 20 January.

Solar Wind / Geomagnetic Activity: The solar wind was symptomatic of connection to a high speed stream, thought to be that emanating from a large southern solar hemisphere 'coronal hole'. The solar wind speed was elevated but near-level, with a brief lull seen during the early UTC evening. The number of particles comprising the solar wind and their associated magnetic field were both slightly elevated but otherwise unremarkable.

The net result of the above solar wind measures was mainly quiet geomagnetic activity, peaking early and late, but well below Minor Storm G1.

Energetic Particles / Solar Radiation: No solar radiation storms were observed.

Four-Day Space Weather Forecast Summary

Solar Activity: Solar activity is expected to be low, with the daily risk of significant flares revised slightly downwards relative to recent guidance given the observed lack of activity and simplifying front-sided sunspot groups. Having said this, the slightly rising trend remains in the four days, with a daily chance of moderate-class flares - the result of the potential arrival of further active regions over the southeastern solar horizon in the period.

Solar Wind / Geomagnetic Activity: A CME associated with a filament lift-off on the afternoon UTC of 14 January is now considered most likely to have passed to no effect at Earth and is removed from the forecast. The CME from the common class flare from 16 January may carry an Earth-directed component,  with a possible glancing blow arriving in the UTC day of Thursday 20 January. This gives perhaps a slight chance of G1 within this UTC day.

The only 'coronal hole' fast wind feature due in the four days is expected to be the current one. A gradual decline toward a slow regime is therefore expected from midweek (independent of the potential CME mentioned above), with increasingly quiet geomagnetic activity expected.

Energetic Particles / Solar Radiation: The weight of sunspot groups and activity in the western solar hemisphere is leading to a raised risk of S1 in the coming four-day period, although the effect is very slight.

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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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