Aurora Info

Aurora Information

So far we are well under way this season and aurora viewings have been very very good indeed , due to frequent weaknesses in the suns magnetic field ,which in turn caused many coronal holes to develop on the surface of the sun that release charged particles into space and were carried towards earth in a strong solar winds , resulting in some fantastic aurora displays , some reaching G1 & G2 storms , even though this is the solar minimum.

 

 

Three recent solar cycles

Solar minimum is the period of least solar activity in the 11 year solar cycle of the sun. During this time, sunspot and solar flare activity diminishes, and often does not occur for days at a time. The date of the minimum is described by a smoothed average over 12 months of sunspot activity, so identifying the date of the solar minimum usually can only happen 6 months after the minimum takes place. Solar minima are not generally correlated with changes in climate but recent studies have shown a correlation with regional weather patterns.

Solar minimum is contrasted with the solar maximum, where there may be hundreds of sunspots

Solar maximum

The current prediction for Sunspot Cycle 24 gives a smoothed sunspot number maximum of about 66 in the Summer of 2013. The smoothed sunspot number has already reached 67 (in February 2012) due to the strong peak in late 2011 so the official maximum will be at least this high. The smoothed sunspot number has been flat over the last four months. We are currently over four years into Cycle 24. The current predicted and observed size makes this the smallest sunspot cycle since Cycle 14 which had a maximum of 64.2 in February 1906. NASA

Solar maximum or solar max is a regular period of greatest Sun activity during the 11-year solar cycle. During solar maximum, large numbers of sunspots appear, and the solar irradiance output grows by about 0.07%.[1] The increased energy output of solar maxima can impact Earth’s global climate, and recent studies have shown some correlation with regional weather patterns.[citation needed]

At solar maximum, the Sun’s magnetic field lines are the most distorted due to the magnetic field on the solar equator rotating at a slightly faster pace than at the solar poles.[citation needed] On average, the solar cycle takes about 11 years to go from one solar maximum to the next, with duration observed varying from 9 to 14 years.

Three recent solar cycles

Large solar flares often occur during a maximum. For example, the solar storm of 1859 struck the Earth with such intensity that the northern lights were visible as far from the poles as Cuba and Hawaii.[2]

See you soon.

What causes the aurora?
The typical aurora is caused by collisions between fast-moving electrons from space combined with the oxygen and nitrogen in earth’s upper atmosphere. The electrons which come from the earth’s magnetosphere, the region of space controlled by earth’s magnetic field, transfer their energy to the oxygen and nitrogen atoms and molecules, making them “excited”.
As the gases return to their normal state, they emit photons, small bursts of energy in the form of light.
When a large number of electrons come from the magnetosphere to bombard the atmosphere, the oxygen and nitrogen can emit enough light for the eye to detect, giving us the beautiful aurora displays, also named the northern lights.
This ghostly light originates at altitudes of 100 to more than 400 km (60 to more than 250 miles) above us.

What causes the aurora?
The typical aurora is caused by collisions between fast-moving electrons from space combined with the oxygen and nitrogen in earth’s upper atmosphere.
The electrons, which come from the earth’s magnetosphere, the region of space controlled by earth’s magnetic field,  transfer their energy to the oxygen and nitrogen atoms and molecules, making them “excited”.
As the gases return to their normal state, they emit photons, small bursts of energy in the form of light.
When a large number of electrons come from the magnetosphere to bombard the atmosphere, the oxygen and nitrogen can emit enough light for the eye to detect, giving us the beautiful auroral displays we call the northern lights.
This ghostly light originates at altitudes of 100 to more than 400 km (60 to more than 250 miles) above us .

 

 The Relationship between the Kp and the Aurora.
From thousands of observations, scientists have determined geographic sub-points for the southern edges of auroral displays.
The curves represent four values of the planetary index (Kp).
As this index increases, the aurora’s southern edge moves southward. 
In this article we briefly explain some of the ideas behind the association of the aurora with geomagnetic activity and a bit about how the ‘K-index’ or ‘K-factor’ works.
The aurora is understood to be caused by the interaction of high energy particles (usually electrons) with neutral atoms in the earth’s upper atmosphere.
These high energy particles can ‘excite’ (by collisions) valence electrons that are bound to the neutral atom.
The ‘excited’ electron can then ‘de-excite’ and return back to its initial, lower energy state, but in the process it releases a photon (a light particle).
The combined effect of many photons being released from many atoms results in the aurora display that you see.
The details of how high energy particles are generated during geomagnetic storms constitute an entire discipline of space science in its own right.
The basic idea, however, is that the Earth’s magnetic field (let us say the ‘geomagnetic field’) is responding to a outwardly propagating disturbance from the Sun.
As the geomagnetic field adjusts to this disturbance, various components of the earth’s field change form, releasing magnetic energy and thereby accelerating charged particles to high energies.
These particles, being charged, are forced to stream along the geomagnetic field lines.
Some end up in the upper part of the earth’s neutral atmosphere and the auroral mechanism begins.
The disturbance of the geomagnetic field may also be measured by an instrument called a magnetometer.
From the operations centre we receive magnetometer data from dozens of observatories in one minute intervals.
The data is received at or near to ‘real-time’ and allows us to keep track of the current state of the geomagnetic conditions.
In order to reduce the amount of data that our customers have to deal with we convert the magnetometer data into three-hourly indices which give a quantitative, but less detailed measure of the level of geomagnetic activity.
The K-index scale has a range from 0 to 9 and is directly related to the maximum amount of fluctuation (relative to a quiet day) in the geomagnetic field over a three-hour interval.
The K-index is therefore updated every three hours and the information is made available to our customers as soon as possible.
The K-index is also necessarily tied to a specific geomagnetic observatory.
For locations where there are no observatories, one can only estimate what the local K-index would be by looking at data from the nearest observatory, but this would be subject to some errors from time to time because geomagnetic activity is not always spatially homogenous.
Another item of interest is that the location of the aurora usually changes geomagnetic latitude as the intensity of the geomagnetic storm changes.
The location of the aurora often takes on an ‘oval-like’ shape and is appropriately called the auroral oval.
A useful map of the approximate location of the auroral oval as a function of the Kp-index was published in the June 1968 copy Sky & Telescope .
The Kp index is derived through by an algorithm that essentially averages the K-indices from several stations.
Note that as a storm becomes more intense, the edge of the auroral boundary typically moves to lower latitudes.
You will notice that Tromsø is allocated right below the Kp Index 0-1 meaning that in clear skies with zero activity we can still see a very faint aurora with the naked eye.
Therefore making Tromsø and surrounding islands, one of the best places on earth to view the auroral display.
See you soon
Marianne Bergli

 

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