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07/14/2017

GEOMAGNETIC STORM WATCH: When & Where Northern Lights Are Possible...

A watch has been issued for likely G2 (Moderate) geomagnetic storm conditions Sunday and early Monday due to the anticipated arrival of a solar coronal mass ejections(CME) from July 14th. While these storms can disrupt navigation systems and power grids, they also create beautiful auroras! An aurora, sometimes referred to as northern lights, is a natural light display in the sky. They form as charged particles in the both solar wind and magnetospheric plasma enter the upper atmosphere, resulting in ionization and excitation. Through this process, light of varying color and complexity dances across the sky. The more intense the energy is as it hits the earth, the greater the chance for northern lights to be visible farther south than normal. Here's the bottom line, auroras MAY be visible Sunday night into early Monday morning across the Upper Midwest and Northeast. Locations between the green and yellow line on the map below have the best chance of seeing the northern lights. Notice that if the energy is more intense than predicted, we may even catch a glimpse in our area! 

G2_0

Image Credit: NOAA

GEOMAGNETIC STORMS

A geomagnetic storm is a major disturbance of Earth's magnetosphere that occurs when there is a very efficient exchange of energy from the solar wind into the space environment surrounding Earth. These storms result from variations in the solar wind that produces major changes in the currents, plasmas, and fields in Earth’s magnetosphere. The solar wind conditions that are effective for creating geomagnetic storms are sustained (for several to many hours) periods of high-speed solar wind, and most importantly, a southward directed solar wind magnetic field (opposite the direction of Earth’s field) at the dayside of the magnetosphere. This condition is effective for transferring energy from the solar wind into Earth’s magnetosphere.

The largest storms that result from these conditions are associated with solar coronal mass ejections (CMEs) where a billion tons or so of plasma from the sun, with its embedded magnetic field, arrives at Earth. CMEs typically take several days to arrive at Earth, but have been observed, for some of the most intense storms, to arrive in as short as 18 hours. Another solar wind disturbance that creates conditions favorable to geomagnetic storms is a high-speed solar wind stream (HSS). HSSs plow into the slower solar wind in front and create co-rotating interaction regions, or CIRs. These regions are often related to geomagnetic storms that while less intense than CME storms, often can deposit more energy in Earth’s magnetosphere over a longer interval.

GeomagneticStormAurora

Image Credit: NOAA

Storms also result in intense currents in the magnetosphere, changes in the radiation belts, and changes in the ionosphere, including heating the ionosphere and upper atmosphere region called the thermosphere. In space, a ring of westward current around Earth produces magnetic disturbances on the ground. A measure of this current, the disturbance storm time (Dst) index, has been used historically to characterize the size of a geomagnetic storm. In addition, there are currents produced in the magnetosphere that follow the magnetic field, called field-aligned currents, and these connect to intense currents in the auroral ionosphere. These auroral currents, called the auroral electrojets, also produce large magnetic disturbances. Together, all of these currents, and the magnetic deviations they produce on the ground, are used to generate a planetary geomagnetic disturbance index called Kp. This index is the basis for one of the three NOAA Space Weather Scales, the Geomagnetic Storm, or G-Scale, that is used to describe space weather that can disrupt systems on Earth.

During storms, the currents in the ionosphere, as well as the energetic particles that precipitate into the ionosphere add energy in the form of heat that can increase the density and distribution of density in the upper atmosphere, causing extra drag on satellites in low-earth orbit. The local heating also creates strong horizontal variations in the in the ionospheric density that can modify the path of radio signals and create errors in the positioning information provided by GPS.  While the storms create beautiful aurora, they also can disrupt navigation systems such as the Global Navigation Satellite System (GNSS) and create harmful geomagnetic induced currents (GICs) in the power grid and pipelines.

Screen-shot-2017-07-14-at-25426-pmpng-c62f2b7c085e80f0

Image Credit: NASA

 

 

-Rick DeLuca

Rick

https://www.facebook.com/RickDeLucaWeather

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So when is the best time for Louisville to see thus phenomenon?

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