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<article language="en">
	<journal>
		<journal_title>Atmospheric Chemistry and Physics Discussions</journal_title>
		<journal_url>www.atmos-chem-phys-discuss.net</journal_url>
		<issn>1680-7367</issn>
		<eissn>1680-7375</eissn>
		<volume_number>9</volume_number>
		<issue_number>5</issue_number>
		<publication_year>2009</publication_year>
	</journal>
	<doi>10.5194/acpd-9-21525-2009</doi>
	<article_url>http://www.atmos-chem-phys-discuss.net/9/21525/2009/</article_url>
	<abstract_html>http://www.atmos-chem-phys-discuss.net/9/21525/2009/acpd-9-21525-2009.html</abstract_html>
	<fulltext_pdf>http://www.atmos-chem-phys-discuss.net/9/21525/2009/acpd-9-21525-2009.pdf</fulltext_pdf>
	<start_page>21525</start_page>
	<end_page>21560</end_page>
	<publication_date>2009-10-13</publication_date>
	<article_title content_type="html">Atmospheric data over a solar cycle: no connection between galactic cosmic rays and new particle formation</article_title>
	<authors>
		<author numeration="1" affiliations="1">
			<name>M. Kulmala</name>
			<email>markku.kulmala@helsinki.fi</email>
		</author>
		<author numeration="2" affiliations="1,2">
			<name>I. Riipinen</name>
		</author>
		<author numeration="3" affiliations="1">
			<name>T. Nieminen</name>
		</author>
		<author numeration="4" affiliations="1">
			<name>M. Hulkkonen</name>
		</author>
		<author numeration="5" affiliations="1,3">
			<name>L. Sogacheva</name>
		</author>
		<author numeration="6" affiliations="1">
			<name>H. E. Manninen</name>
		</author>
		<author numeration="7" affiliations="1">
			<name>P. Paasonen</name>
		</author>
		<author numeration="8" affiliations="1">
			<name>T. PetÃ¤jÃ¤</name>
		</author>
		<author numeration="9" affiliations="1">
			<name>M. Dal Maso</name>
		</author>
		<author numeration="10" affiliations="1">
			<name>P. P. Aalto</name>
		</author>
		<author numeration="11" affiliations="3">
			<name>A. Viljanen</name>
		</author>
		<author numeration="12" affiliations="4">
			<name>I. Usoskin</name>
		</author>
		<author numeration="13" affiliations="1">
			<name>R. Vainio</name>
		</author>
		<author numeration="14" affiliations="5">
			<name>S. Mirme</name>
		</author>
		<author numeration="15" affiliations="5">
			<name>A. Mirme</name>
		</author>
		<author numeration="16" affiliations="6">
			<name>A. Minikin</name>
		</author>
		<author numeration="17" affiliations="6">
			<name>A. Petzold</name>
		</author>
		<author numeration="18" affiliations="5">
			<name>U. HÃµrrak</name>
		</author>
		<author numeration="19" affiliations="7">
			<name>C. PlaÃŸ-DÃ¼lmer</name>
		</author>
		<author numeration="20" affiliations="8">
			<name>W. Birmili</name>
		</author>
		<author numeration="21" affiliations="3">
			<name>V.-M. Kerminen</name>
		</author>
	</authors>
	<affiliations>
		<affiliation numeration="1" content_type="html">University of Helsinki, Helsinki, Finland</affiliation>
		<affiliation numeration="2" content_type="html">Carnegie Mellon University, Pittsburgh, Pennsylvania, USA</affiliation>
		<affiliation numeration="3" content_type="html">Finnish Meteorological Institute, Helsinki, Finland</affiliation>
		<affiliation numeration="4" content_type="html">SodankylÃ¤ Geophysical Observatory (Oulu Unit), University of Oulu, SodankylÃ¤, Finland</affiliation>
		<affiliation numeration="5" content_type="html">University of Tartu, Tartu, Estonia</affiliation>
		<affiliation numeration="6" content_type="html">Deutsches Zentrum fÃ¼r Luft- und Raumfahrt (DLR), Wessling, Germany</affiliation>
		<affiliation numeration="7" content_type="html">Meteorologisches Observatorium Hohenpeissenberg, Deutscher Wetterdienst (DWD), Hohenpeissenberg, Germany</affiliation>
		<affiliation numeration="8" content_type="html">Leibniz Institute for Tropospheric Research, Leipzig, Germany</affiliation>
	</affiliations>
	<abstract content_type="html">Aerosol particles affect the Earth&apos;s radiative balance by directly scattering and absorbing
solar radiation and, indirectly, through their activation into cloud droplets. Both effects
are known with considerable uncertainty only, and translate into even bigger uncertainties
in future climate predictions. More than a decade ago, variations in galactic cosmic rays
were suggested to closely correlate with variations in atmospheric cloud cover and therefore
constitute a driving force behind aerosol-cloud-climate interactions. Later, the enhancement
of atmospheric aerosol particle formation by ions generated from cosmic rays was proposed as
a physical mechanism explaining this correlation. Here, we report unique observations on
atmospheric aerosol formation based on measurements at the SMEAR II station, Finland, over
a solar cycle (years 1996â€“2008) that shed new light on these presumed relationships. Our
analysis shows that none of the quantities related to aerosol formation correlates with the
cosmic ray-induced ionisation intensity (CRII). We also examined the contribution of ions to
new particle formation on the basis of novel ground-based and airborne
observations. A consistent result is that ion-induced formation contributes typically less
than 10% to the number of new particles, which would explain the missing correlation
between CRII and aerosol formation. Our main conclusion is that galactic cosmic rays appear
to play a minor role for atmospheric aerosol formation, and so for the connected
aerosol-climate effects as well.</abstract>
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