Does each Chanukah candle need to be individually lit?

Question

Let's say someone lit the oil and set it on fire, or lit one candle and a spark or the flame from one candle lit other candles next to it. Is this a permissible lighting or does each candle need to be manually lit from the shamash?

Answer 1

Question: Is this a permissible lighting or does each candle need to be manually lit from the shamash?

Answer: Each candle needs to be lit manually with intent.

Whether it needs to be from the shamash or from another candle is already discussed in סימן תרעד with the Machaber being lenient and the Remo suggesting one be stringent.

א מַדְלִיקִין נֵר חֲנֻכָּה מִנֵּר חֲנֻכָּה, וְדַוְקָא לְהַדְלִיק (א) זֶה מִזֶּה בְּלֹא אֶמְצָעִי, אֲבָל לְהַדְלִיק זֶה מִזֶּה עַל יְדֵי נֵר שֶׁל חֹל, אָסוּר; וְיֵשׁ מַתִּירִים גַּם בָּזֶה, אֶלָּא אִם כֵּן הוּא בְּעִנְיָן שֶׁיֵּשׁ לָחוּשׁ שֶׁיִּכְבֶּה הַנֵּר שֶׁל חֹל קֹדֶם שֶׁיַּדְלִיק נֵר אַחֵר שֶׁל חֲנֻכָּה.‏
הגה: וְנָהֲגוּ לְהַחְמִיר בְּנֵרוֹת חֲנֻכָּה שֶׁלֹּא לְהַדְלִיק אֲפִלּוּ מִנֵּר לְנֵר, דְּעִקַּר מִצְוָתוֹ אֵינוֹ אֶלָּא נֵר אֶחָד וְהַשְּׁאָר אֵינוֹ לְמִצְוָה כָּל כָּךְ לָכֵן אֵין לְהַדְלִיק זֶה מִזֶּה...‏

Regarding the question of: Each candle needs to be lit manually with intent:

In סימן תרעה the Shulchan Aruch paskens that הַדְלָקָה עוֹשָׂה מִצְוָה - the act of lighting is the main part of the Mitzva of Chanuka candles.

This alone should answer the question: The Mitzva of Chanuka is to actively light the relevant number of candles for each night.

The Aruch haShulchan (ibid) goes into more detail and brings an even bigger proof: the Gemara in Shabbat (23a) says that if a candle is lit for the Mitzva of Chanuka and (24 hours later) is still burning the next night, it doesn't count towards the next night's candles, but needs to be extinguished and lit again.

ולא עוד, אלא אפילו היתה דלוקה לשם מצות נר חנוכה, ודולקת מעת לעת למחר – צריך לכבותה ולהדליקה מחדש. וכך אמרו חכמינו ז''ל (שם): עששית שהיתה דולקת כל היום, שהיתה דלוקה מערב שבת לשם מצות נר חנוכה למוצאי שבת – מכבה ומדליקה לשם מצוה. ‏

A peek at the Gemara brings another proof that the candles have to be actively it- which the Aruch Hashuclan mentions later - i.e.:

והשתא דאמרינן הדלקה עושה מצוה הדליקה חרש שוטה וקטן לא עשה ולא כלום‏

As Sefaria translates:

And, the Gemara remarks, now that we say that lighting accomplishes the mitzva, there are practical ramifications. If a deaf-mute, an imbecile, or a minor, all of whom are of limited intellectual capacity and not obligated in mitzvot, kindled the Hanukkah light, he did nothing in terms of fulfilling the mitzva.

It follows that if a candle lit itself, it cannot be considered to be a Chanuka candle.

Answer 2

Kitzur Shulchan Aruch 139:9 tells us that the candles of the Chanukah menorah should be distanced away from each other so that the heat of the candles do not melt eachother and the wax from two candles combines. The reason is because this might give the menorah lights the appearance of a torch, which is not kosher as a menorah light.

The candles should be positioned in one row of equal height, not with one candle high and one candle low. There should be a space between each light, so that the flames do not draw close to one another, which would give the appearance of a torch. With wax candles, there should be enough space between each one so that they are not heated by one another, causing the wax to drip and the candles to be ruined.

(From the ArtScroll Kitzur Shulchan Aruch)