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We have studied various complex motions of the irregular dust grains immersed in non-uniformly magnetized plasma. The cylindrical magnet that we used for experiments significantly alters the radial distribution of the sheath potential which confines the negatively charged grains. Grains are horizontally illuminated by a 50 mW, 532 nm laser sheet and imaged by a CCD camera from the upper transparent electrode. Hypocycloid and epicycloid motions of grains are observed for the first time as far as we know. Cuspate cycloid motions, circle motion, wave motion, and stationary grains are also observed. Their trajectories can be obtained by using long-time exposure, and the characteristic parameters of the grain movement are measured by using the image processing with MATLAB. Though the dust grains can move around the magnet steadily in various trajectories, the induced magnetic field is too weak to give rise to cycloid motions of grains. Then we propose a new mechanism that an inverse Magnus force induced by the spin of the irregular grains plays an important role in their cycloid motions. The pollen pini we used for experiment is not a regular microsphere, there is a symmetry in the shape. On the basis of Bernoulli principle, the pressure difference between the left and right side of the forward moving grains produces the inverse Magnus effect. Additional comparison experiments with regular microspheres are also performed to confirm that the cycloid motions are distinctive features of an irregular dust grain immersed in the plasma. The periodical change of the cyclotron radius as the grain travels would result in the (cuspate) cycloid motions, and the maximal value of angular velocity of spin is about 105 rad/s. Our experimental observations can be well explained based on the force analysis in 2D horizontal plane.
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Keywords:
- dusty plasma /
- irregular grains /
- inverse Magnus force
[1] Morfill G E, Ivlev A V 2009 Rev. Mod. Phys. 81 1353
[2] Amatucci W E, Walker D N, Gatling G, Scime E E 2004 Phys. Plasmas 11 2097
[3] Huang F, Ye M F, W L 2004 Chin. Sci. Bull. 49 2150 (in Chinese) [黄峰, 叶茂福, 王龙 2004 科学通报 49 2150]
[4] Konopka U, Samsonov D, Ivlev A V, Goree J, Steinberg V 2000 Phys.Rev. E 61 1890
[5] Hou L J, Wang Y N, Mikovic 2005 Phys. Plasmas 12 042104
[6] Liu D Y, Wang D Z, Liu J Y 2000 Acta Phys. Sin. 49 1094(in Chinese) [刘德泳, 王德真, 刘金远 2000 49 1094]
[7] Konopka U, Samsonov D, Ivlev A V, Goree J, Steinberg V, Morfill G E 2000 Phys. Rev. E 61 1890
[8] Carstensen J, Greiner F, Hou L J, Maurer H, Piel A 2009 Phys. Plasma 16 013702
[9] Hong X R, Duan W S, Sun J A, Shi Y R, Lv K P 2003 Acta Phys. Sin. 52 2671(in Chinese) [洪学仁, 段文山, 孙建安, 石玉任, 吕克璞 2003 52 2671]
[10] Tsytovich V N, Sato N, Morfill G E 2003 New J. Phys. 5 43
[11] Karasev V Yu, Dzlieva E S, Eikhvald A I, Ermolenko M A, Golubev M S, Ivanov A Yu 2009 Phys. Rev. E 79 026406
[12] Karasev V Yu, Dzlieva E S, Eikhvald A I, Ermolenko M A, Golubev M S, Ivanov A Yu 2009 J. Plasma Fusion Res. Series 8 312
[13] Krasheninnikov S I, Shevchenko V I, Shukla P K 2007 Phys. Lett. A 361 133
[14] Juan W T, I L 1998 Phys. Rev. Lett. 80 3073
[15] Zou X, liu J Y, Wang Z X, Gong Y, Liu Y, Wang X G 2004 Acta Phys. Sin. 53 3409(in Chinese) [邹秀, 刘金远, 王正汹, 宫野, 刘悦, 王晓钢 2004 53 3409]
[16] Karasev V Yu, Dzlieva E S, Ivanov A Yu, Eikhvald A I 2006 Phys. Rev. E 74 066403
[17] Holland D L, Fried B D, Morales G J 1993 Phys. Fluids B 5 1723
[18] Kaw P K, Nishikawa K, Sato N 2002 Phys. Plasma 9 387
[19] Paeva G V, Dahiya R P, Kroesen G M W, Stoffels W W 2004 IEEE Trans. Plasma Sci. 32 601
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[1] Morfill G E, Ivlev A V 2009 Rev. Mod. Phys. 81 1353
[2] Amatucci W E, Walker D N, Gatling G, Scime E E 2004 Phys. Plasmas 11 2097
[3] Huang F, Ye M F, W L 2004 Chin. Sci. Bull. 49 2150 (in Chinese) [黄峰, 叶茂福, 王龙 2004 科学通报 49 2150]
[4] Konopka U, Samsonov D, Ivlev A V, Goree J, Steinberg V 2000 Phys.Rev. E 61 1890
[5] Hou L J, Wang Y N, Mikovic 2005 Phys. Plasmas 12 042104
[6] Liu D Y, Wang D Z, Liu J Y 2000 Acta Phys. Sin. 49 1094(in Chinese) [刘德泳, 王德真, 刘金远 2000 49 1094]
[7] Konopka U, Samsonov D, Ivlev A V, Goree J, Steinberg V, Morfill G E 2000 Phys. Rev. E 61 1890
[8] Carstensen J, Greiner F, Hou L J, Maurer H, Piel A 2009 Phys. Plasma 16 013702
[9] Hong X R, Duan W S, Sun J A, Shi Y R, Lv K P 2003 Acta Phys. Sin. 52 2671(in Chinese) [洪学仁, 段文山, 孙建安, 石玉任, 吕克璞 2003 52 2671]
[10] Tsytovich V N, Sato N, Morfill G E 2003 New J. Phys. 5 43
[11] Karasev V Yu, Dzlieva E S, Eikhvald A I, Ermolenko M A, Golubev M S, Ivanov A Yu 2009 Phys. Rev. E 79 026406
[12] Karasev V Yu, Dzlieva E S, Eikhvald A I, Ermolenko M A, Golubev M S, Ivanov A Yu 2009 J. Plasma Fusion Res. Series 8 312
[13] Krasheninnikov S I, Shevchenko V I, Shukla P K 2007 Phys. Lett. A 361 133
[14] Juan W T, I L 1998 Phys. Rev. Lett. 80 3073
[15] Zou X, liu J Y, Wang Z X, Gong Y, Liu Y, Wang X G 2004 Acta Phys. Sin. 53 3409(in Chinese) [邹秀, 刘金远, 王正汹, 宫野, 刘悦, 王晓钢 2004 53 3409]
[16] Karasev V Yu, Dzlieva E S, Ivanov A Yu, Eikhvald A I 2006 Phys. Rev. E 74 066403
[17] Holland D L, Fried B D, Morales G J 1993 Phys. Fluids B 5 1723
[18] Kaw P K, Nishikawa K, Sato N 2002 Phys. Plasma 9 387
[19] Paeva G V, Dahiya R P, Kroesen G M W, Stoffels W W 2004 IEEE Trans. Plasma Sci. 32 601
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