Aurora

<body topmargin=0 leftmargin=0 marginheight=0 marginwidth=0> <table cellpadding=0 cellspacing=0 border=0 height="100%"><tr> <td valign="top" width=168 BGCOLOR="#000000" TEXT="#F7F7FF" background="13ea11c3.png"> <div> <A HREF="http://www.petergarbett.com" TARGET="_top" TITLE="http://www.petergarbett.com"><B><IMG SRC="14f64510.png" border=0 width="100" height="81" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></B></A></div> <div> <A HREF="https://www.petergarbett.com" TARGET="_top" TITLE="https://www.petergarbett.com"><B>Home</B></A></div> <bR> <div> The Aurora Borealis, or 'Northern Lights' also has its southern hemisphere counterpart, the Aurora Australis or 'Southern Lights'. Usually associated with higher geomagnetic latitudes than England, it may, however, be seen from my observatory at times of intense geomagnetic storms. We now undersatnd that such events are caused by a large flux of charged particles ejected from the Sun penetrating the Earth's magnetosphere and impinging on the Earth's upper atmosphere. This burst of charged particles is often associated with a major solar flare and so called 'coronal mass ejections' from the Sun.</div> </td> <td valign="top" width="100%" BGCOLOR="#000000" TEXT="#F7F7FF"> <div> <B>Aurora</B><FONT SIZE="7" COLOR="#FFFF00" FACE="Times New Roman" > </FONT></div> <div> <IMG SRC="00758020.png" border=0 width="600" height="2" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></div> <bR> <div> <B><U>6th-7th April 2000</U></B></div> <bR> <div> As seen from Sharnbrook: a great display!</div> <bR> <div> Photos were taken from 20:51 - 01:10 UTC, with OM10 SLR and mostly 1600 ASA Fuji Provia Film.</div> <div> The display became so remarkable, the whole sky, including the south aspect was full of aurorae!</div> <bR> <bR> <div> <IMG SRC="196b17a0.jpg" border=0 width="177" height="122" ALIGN="BOTTOM" HSPACE="0" VSPACE="0">    <IMG SRC="194b17a0.jpg" border=0 width="177" height="122" ALIGN="BOTTOM" HSPACE="0" VSPACE="0">    <IMG SRC="18aae790.jpg" border=0 width="174" height="121" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></div> <bR> <div> <IMG SRC="192b1060.jpg" border=0 width="177" height="262" ALIGN="BOTTOM" HSPACE="0" VSPACE="0">    <IMG SRC="191b1f90.jpg" border=0 width="177" height="249" ALIGN="BOTTOM" HSPACE="0" VSPACE="0">    <IMG SRC="15ab1100.jpg" border=0 width="177" height="272" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></div> <bR> <div> <IMG SRC="190b17a0.jpg" border=0 width="177" height="122" ALIGN="BOTTOM" HSPACE="0" VSPACE="0">    <IMG SRC="18ead750.jpg" border=0 width="173" height="117" ALIGN="BOTTOM" HSPACE="0" VSPACE="0">    <IMG SRC="19eb18b0.jpg" border=0 width="177" height="139" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></div> <bR> <div> <IMG SRC="18dec9c0.jpg" border=0 width="236" height="156" ALIGN="BOTTOM" HSPACE="0" VSPACE="0">    </div> <bR> <bR> <bR> <bR> <div> <IMG SRC="1a82e3d0.jpg" border=0 width="558" height="829" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></div> <bR> <div> Cygnus up to Draco</div> <bR> <bR> <bR> <bR> <bR> <bR> <div> <IMG SRC="1a93e1b0.jpg" border=0 width="830" height="539" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></div> <bR> <div> Cygnus</div> <bR> <bR> <bR> <bR> <bR> <bR> <bR> <div> <IMG SRC="1aa930c0.jpg" border=0 width="659" height="524" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></div> <bR> <bR> <bR> <bR> <div> <IMG SRC="1ab3c300.jpg" border=0 width="828" height="560" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></div> <bR> <div> Lyra and Cygnus</div> <bR> <bR> <bR> <bR> <bR> <bR> <div> <IMG SRC="1ac3c300.jpg" border=0 width="828" height="560" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></div> <bR> <bR> <bR> <bR> <bR> <bR> <div> <IMG SRC="1ad34310.jpg" border=0 width="820" height="561" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></div> <bR> <div> Bootes</div> <bR> <bR> <bR> <bR> <div> <IMG SRC="1ae281c0.jpg" border=0 width="808" height="540" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></div> <bR> <bR> <bR> <bR> <bR> <bR> <bR> <bR> <bR> <bR> <bR> <bR> <bR> <bR> <div> <IMG SRC="1b035360.jpg" border=0 width="821" height="566" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></div> <bR> <bR> <bR> <bR> <bR> <bR> <bR> <div> <IMG SRC="1b13d2e0.jpg" border=0 width="829" height="558" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></div> <bR> <bR> <bR> <bR> <bR> <bR> <bR> <div> <IMG SRC="1b231340.jpg" border=0 width="817" height="564" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></div> <bR> <bR> <bR> <bR> <bR> <bR> <div> <IMG SRC="1b332380.jpg" border=0 width="562" height="824" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></div> <bR> <bR> <bR> <bR> <bR> <div> <IMG SRC="1b436490.jpg" border=0 width="566" height="841" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></div> <bR> <div> Corona Borealis and Hercules</div> <bR> <bR> <bR> <bR> <bR> <bR> <bR> <div> <IMG SRC="1b53d2d0.jpg" border=0 width="829" height="557" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></div> <bR> <bR> <bR> <bR> <bR> <bR> <bR> <bR> <div> <IMG SRC="1b60b190.jpg" border=0 width="779" height="537" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></div> <bR> <bR> <bR> <bR> <div> <IMG SRC="1b72d240.jpg" border=0 width="813" height="548" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></div> <bR> <bR> <bR> <bR> <div> <IMG SRC="1b80a2e0.jpg" border=0 width="778" height="558" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></div> <bR> <bR> <bR> <bR> <div> <IMG SRC="1b9363a0.jpg" border=0 width="822" height="570" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></div> <bR> <bR> <bR> <bR> <bR> <bR> <bR> <bR> <div> <IMG SRC="1ba33290.jpg" border=0 width="563" height="809" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></div> <bR> <div> Auriga and Gemini (dodgy focus due to ill-fitting 28mm F2.8 lens!)</div> <div> 21:52 UTC; 1600 ASA Fuji Super HG film on OM10 SLR</div> <bR> <bR> <bR> <bR> <bR> <div> <IMG SRC="1bb33460.jpg" border=0 width="563" height="838" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></div> <bR> <bR> <div> 1600 ASA Fuji Super HG film on OM10 SLR</div> <bR> <bR> <bR> <bR> <div> <B><U>15th July 2000</U></B></div> <bR> <div> As seen from Sharnbrook, remarkably in the light of a nearly Full Moon!</div> <bR> <bR> <div> <IMG SRC="19576ab0.jpg" border=0 width="118" height="171" ALIGN="BOTTOM" HSPACE="0" VSPACE="0">                <IMG SRC="193b1010.jpg" border=0 width="177" height="257" ALIGN="BOTTOM" HSPACE="0" VSPACE="0">            <IMG SRC="18bb17c0.jpg" border=0 width="177" height="124" ALIGN="BOTTOM" HSPACE="0" VSPACE="0">          </div> <div>                                       <IMG SRC="15fb1760.jpg" border=0 width="177" height="118" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></div> <bR> <bR> <div>              <IMG SRC="1a19dce0.jpg" border=0 width="413" height="206" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></div> <div> <B>Above left</B>: Aurora Borealis 15th July 2000   <B>Above right</B>: sunspot group that caused the aurora as seen on 13th July 2000.</div> <bR> <bR> <bR> <bR> <div> <B><U>Early hours of 27th August 1998</U></B></div> <bR> <div> As seen on holiday in the Lleyn Peninsula, North Wales.</div> <bR> <div> <IMG SRC="184b1890.jpg" border=0 width="177" height="137" ALIGN="BOTTOM" HSPACE="0" VSPACE="0">         <IMG SRC="19cb17a0.jpg" border=0 width="177" height="122" ALIGN="BOTTOM" HSPACE="0" VSPACE="0">        </div> <bR> <bR> <div> <IMG SRC="19bb17a0.jpg" border=0 width="177" height="122" ALIGN="BOTTOM" HSPACE="0" VSPACE="0">         <IMG SRC="198b17a0.jpg" border=0 width="177" height="122" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></div> <bR> <bR> <div> <B><U>29th October 2003</U></B></div> <bR> <div> As seen from Sharnbrook following an unexpected surge in solar activity. </div> <div> The geomagnetic storm was subsiding by the time it was dark, so this is the mere tail</div> <div> end of a good display.</div> <bR> <div> <IMG SRC="187e85a0.jpg" border=0 width="232" height="346" ALIGN="BOTTOM" HSPACE="0" VSPACE="0">     <IMG SRC="1a362e90.jpg" border=0 width="354" height="233" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></div> <bR> <div> <IMG SRC="1a48e070.jpg" border=0 width="398" height="263" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></div> <bR> <bR> <bR> <bR> <div> <B><U>My first experiences of the aurora</U></B></div> <bR> <div> As seen from Barton-le-Clay and sketched in one of my log books.</div> <div> Forgive the spelling error!</div> <bR> <bR> <div> <IMG SRC="1a537bf0.jpg" border=0 width="567" height="447" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></div> <bR> <div> <IMG SRC="1a63dd70.jpg" border=0 width="573" height="471" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></div> <bR> <div> <IMG SRC="1a737620.jpg" border=0 width="567" height="354" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></div> <bR> <bR> <div> <B><U>Auroral Types and Colours</U></B></div> <bR> <div> <B>G</B></div> <div> <B>glow</B></div> <bR> <div> Glow with no other structure, often lying low above poleward horizon. This may often </div> <div> be confused with light pollution!</div> <bR> <div> <IMG SRC="19ab1740.jpg" border=0 width="177" height="116" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></div> <bR> <bR> <div> <B>A</B></div> <div> <B>arc</B></div> <bR> <div> Arc structure, an arch of light spanning east-west across the sky. May be homogeneous</div> <div> (HA) or rayed (RA).</div> <bR> <div> <IMG SRC="19cb17a0.jpg" border=0 width="177" height="122" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></div> <bR> <bR> <div> <B>B</B></div> <div> band</div> <bR> <div> Folded, ribbon-like structure, often developing from an arc. May have HB or RB.</div> <bR> <div> <IMG SRC="197eca30.jpg" border=0 width="236" height="163" ALIGN="BOTTOM" HSPACE="0" VSPACE="0">        <IMG SRC="153b17a0.jpg" border=0 width="177" height="122" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></div> <bR> <bR> <div> <IMG SRC="198b17a0.jpg" border=0 width="177" height="122" ALIGN="BOTTOM" HSPACE="0" VSPACE="0">        <IMG SRC="162b17a0.jpg" border=0 width="177" height="122" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></div> <bR> <bR> <div> <IMG SRC="172b1010.jpg" border=0 width="177" height="257" ALIGN="BOTTOM" HSPACE="0" VSPACE="0">        <IMG SRC="154b1060.jpg" border=0 width="177" height="262" ALIGN="BOTTOM" HSPACE="0" VSPACE="0">        <IMG SRC="1a0b1100.jpg" border=0 width="177" height="272" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></div> <bR> <bR> <bR> <div> <B>R</B></div> <div> <B>rays</B></div> <bR> <div> Rays may sometimes be seen in isolation or bundles when no other aurora is present.</div> <bR> <bR> <div> <IMG SRC="155b1f90.jpg" border=0 width="177" height="249" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></div> <bR> <bR> <div> <B>V</B></div> <div> <B>veil</B></div> <bR> <div> A background veil which sometimes pervades the sky during auroral displays.</div> <bR> <div> <IMG SRC="189b1760.jpg" border=0 width="177" height="118" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></div> <bR> <bR> <bR> <div> <B>P</B></div> <div> <B>patches</B></div> <bR> <div> Discrete patches (sometimes referred to as 'surfaces') of auroral light. May appear </div> <div> as HP or RP.</div> <bR> <div> <IMG SRC="188b17a0.jpg" border=0 width="177" height="122" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></div> <bR> <bR> <div> <B>corona</B></div> <bR> <div> <IMG SRC="18ead750.jpg" border=0 width="173" height="117" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></div> <bR> <div> <IMG SRC="19eb18b0.jpg" border=0 width="177" height="139" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></div> <div> I couldn't resist this last one! The corona in Corona Borealis!</div> <bR> <div> <B>N</B></div> <bR> <div> Auroral light, not identifiable, seen for example through cloud.</div> <bR> <bR> <div> <B><U>The Colour of Aurorae</U></B></div> <bR> <div> The coloured light of aurorae is produced by the excitation of atmospheric atoms and </div> <div> molecules when energetic electrons from the Sun (often produced in solar flares) </div> <div> penetrate the Earth's protective magnetic 'shield' known as the magnetosphere.</div> <bR> <div> <B>Green Aurorae</B></div> <div> Due to emission at a wavelength of 557.7nm from excited oxygen atoms* (OI) at an </div> <div> altitude between about 90 and 150km. In mid-latitudes, this is the lowest level aurora </div> <div> and can be seen in some of my photos lying below the red aurora.</div> <div> *Oxygen molecules (O2) are split into atomic oxygen at altitudes above about 80km </div> <div> by solar UV. This is called <I>photodissociation</I>.</div> <bR> <div> <B>Red Aurorae</B></div> <div> At altitudes above 150km the aurora produced by excited oxygen atoms (OI) is red </div> <div> rather than green as it is caused by emission lines at 630 and 636.4nm. Since red </div> <div> aurorae are produced at higher altitudes, it is common during an auroral display to see </div> <div> the red component of the aurora sitting on top of the green.</div> <bR> <div> The colours appear at different altitudes because the electronic transition responsible for </div> <div> the production of red light has a long lifetime of 110s, whereas for green it is only 0.74s. </div> <div> Below about 150km, the atmosphere is dense enough that the atoms are disturbed by </div> <div> collisions with other atoms and electrons before the red emission occurs, and so only </div> <div> green may be seen. Above 150km, green is still emitted but is swamped by the red </div> <div> emissions. Below about 90km, even the atoms emitting green light are disturbed by </div> <div> collisions before they can do so.</div> <bR> <div> During very intense displays, keep an eye out for a red tinge low down. This is due to </div> <div> emission from atomic nitrogen at 70 - 100km altitude.</div> <bR> <div> <B>Violet-Purple Aurorae</B></div> <div> At a typical altitude of 1000km, nitrogen molecules, ionised by UV from the Sun (N2+) </div> <div> produces violet purple emissions when excited by incoming accelerated electrons. This </div> <div> is the uppermost region of an auroral display and may only be in the earth's shadow </div> <div> (and therefore visible) at certain times of the year.</div> <bR> <bR> <bR> <bR> </td> </tr></table></body>